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Dr. Jim Rosso
jlrosso@aol.com

Learning Science through the Study of Birds


The White-tailed Kite

A study of how a bird almost became extinct in the 1930s, some 30 years before its wetlands habitat started disappearing faster than it ever had before, and 30 years before the human population started growing rapidly. The irony is that the White-tailed Kite's population became more stabilized during the time that the human population was rapidly growing and the habitat was disappearing. Over a thirty year period California eliminated approximately 90% of its wetlands, and the White-tailed Kite population grew.

 

Table of Contents

Preface

 
Part One - The Case
Chapter One

The Natural History of the White Tailed Kite

Chapter Two

The Historical Account of the Kite's Distribution

Chapter Three

The Christmas Bird Count Records

Chapter Four

The Northern Harrier- Consideration of a Similar Species

Chapter Five

The California Vole

Chapter Six

Introduction to Population Ecology

Chapter Seven

Notes on Hunting

Part Two - The Lesson Plans

1. How many voles

2. The Real Estate Question

3. Develop a scenario

4. Average, Mean, Mode

5. Graphing the results

6. Population Dynamics

7. Double or Nothing

8. Profile of a CBC

9. History of California Agriculture

10. Sim City meets the White-tailed Kite

11. White-tailed Kite as an Indicator Species

12. Microtene Bust


Preface

Appendices

Lesson Plans

The Bibliography

Top

In 1960 the author was invited to go on a hastily planned field trip to an area just north of Marin County in northern California. A White-tailed Kite (Elanus leucurus) had been spotted and people were gathering to go take a look at this rare bird. For many it would be their first look. We eventually found the kite flying around a wet grassland looking for its favorite food, the California Vole (Microtus californicus).

The history of this bird in the United States and especially in California, is unique in the study of birds. In historical writings from 1886 through 1945, ornithologists were predicting the demise of this species. As Grinnell (1915) a California ornithologist, put it, the White-tailed Kite was due for "an early extinction."

Current records show that the kite's numbers have stabilized over the past 40 years. In 1927 Ralph Hoffman anticipated that there were only fifty pair of the birds in the entire state. Seventy years later there is good evidence that there are well over 2000 birds in California; from 100 birds to 2000 birds in seventy years.

How the White-tailed Kite managed to not become extinct and instead become a fairly common bird in its favorite habitat is a modern-day ecological mystery.

There are two goals of the White-tailed Kite Curriculum: (1) to develop a portrait of a species returning from the brink of extinction, and (2) to set up a curriculum that would introduce the student to using science to explore the dynamics of the White-tailed Kite.


 Introduction and Purpose of this Site

The theme running through this book is that the structure of the environment, the morphology of the species, the economy of species behavior, and the dynamics of population changes are the four essential ingredients of all interesting biogeographical patterns.

Robert MacArthur, Geographical Ecology - Patterns in the Distribution of Species


The White-tailed Kite is a good opportunity for a study of biogreographical patterns. It is very connected to a specific type of habitat, the wetlands. The structure of the enviornment is important. The morphology, the structure of the Kite is well adapted to the wetlands habitat.

The White-tailed Kite is a specialist. A specialist is a species that has very specific requirments. A crow is not a specialist; it is a generalist. It can live in a variety of different habitats, eat whatever food is available, and can breed in a wide range of circumstances. A specialist is a species that has rigid requirements. An Osprey is a specialist. It eats only fish that it hunts from the water. The Snail Kite is a specialist as it eats only snails. The White-tailed Kite feeds primarily on voles, lives primarily in wetlands, and has a fairly specific range that it lives.

It is a medium-sized raptor whose morphology - wing structure, sharp talons, and accurate eye - combine to make it a skilled hunter. The kite is buoyant and quick and uses the wind to its advantage to catch its daily minimum of voles. It is found in grasslands lower than 2000 feet that are the results of fresh water supplies. It is so well adapted to its environment that it is one of few raptors that generally doesn't migrate. When the vole population explodes the kite can sometimes breed twice in the season to take full advantage of the increased number of voles.

The White-tailed Kite has gone from abundant to almost extinct to locally common over the past 100 years. As wetlands have disappeared and forest became farms, we have become aware of how the effect of modern civilization has been dangerous to our fellow animals. In the midst of these concerns it is intriguing to come across a species that was anticipated to become extinct and did not. The anticipation of its extinction happened even before its breeding grounds started disappearing in the later part of the twentieth century. Why did it not become extinct? What were the factors that enabled a bird that had practically disappeared to once again become a regularly breeding resident in a disapearing habitat?

The goal of The White-tailed Kite Curriculum is to create a science curriculum that explores some of the data involved in the history of this bird. Science is the study of the forces at work in our world. Generally the study of science does not utilize population studies of a bird as an approach to understand the broad truths of science.

Part One of The White Tailed Kite Curriculum introduces the natural history of the White-tailed Kite. It then provides an historical account of the status of this bird.

In order to document the status of this bird we will use numbers provided by the Christmas Bird Counts (CBC). CBCs have been conducted for over 100 years. By its longevity alone the information provided has become valuable data. Within California it is possible to study the density of kites in over 30 plots for over 30 years. The author is pleased to note that he participated in some of these counts.

In addition to the historical accounts and the CBC numbers, other chapters are utilized to introduce the science of population ecology and to compare the status of the White-tailed Kite and a very similar raptor, the Northern Harrier. What does the success of the Northern Harrier tell us about the White-tailed Kite? Can either species be considered a keystone species or an indicator species? How different is the Northern Harrier's habitat selection from the White-tailed Kite's habitat selection? What does the success of the Northern Harrier tell us about the White-tailed Kite? 

From the USGS Glossary of Avian Conservation Terms - "Biogeography - the study of the geographic distribution of organisms, both past and present". We have 100 years of CBCs to develop a sketch of how the White-tailed Kite has survived over the past 100 years. The number of CBCs has grown at the same time that the population of the kite has grown. But we have good resources to show that the number of kites seen between 1900 and 1930 on the CBCs accurately represents the number of kites in California. It is a rare situation to have this kind of data that follows the rejuvenation of a species.

Part Two of the White-tailed Kite Curriculum takes the content from Part One and creates lesson plans for the independent student. The goal is to introduce a different approach to an ecological study.

 


Chapter 1 - The Natural History of the White-tailed Kite
Appendices
Lesson Plans
Top
Avian Conservation Glossary


The following sections are from a variety of different sources, that when combined form a general natural history of the White-tailed Kite. The natural history notes include six sections: Kites in general, breeding, food, hunting, habitat and distribution.

Kites in general

From Living Birds of the World :

The most primitive of the eight groups or subfamilies of diurnal birds of prey are the kites, which occur in most of the warmer regions of the world. They are long-winged and mostly long-tailed birds that are particularly adept at soaring, circling and gliding. They habitually work their way languidly over semi-open country, often in groups, their wings cocked at a slight dihedral angle.

From, Birds of Prey of the World p. 207

The "black shoulder" is the common marking of this group, which is widely but erratically distributed throughout the warmer parts of the globe in steppe, desert, savanna, and the tropical forest. Four species are very similar, except for the slight variations in the underwing patterns. Three of them are considered by some ornithologists to be geographical representatives of a single species.

White-tailed Kite (Elanus leucurus) formerly Black-shouldered Kite (Elanus caeruleus). Between 1961 and 1980 the White-tailed Kite was temporarily named the Black-shouldered Kite.

 

Breeding

Gillard, Living Birds of the World:

The White-tailed Kite (Elanus leucurus) about 16 inches in length, ranges from the southern borders of the United States through much of South America. Both sexes participate in nest construction, and four eggs are normally laid. Incubation requires up to 32 days, with both parents taking part. The young remain on the nest for about a month and then return to it for some time thereafter to obtain food.

 

From, Birds of Prey of the World , p. 209

The White-tailed Kite builds a bulky nest of small fine twigs, deeply hollowed, and about 18 to 59 feet high in the top of an oak, willow, eucalyptus, or other deciduous tree. Both sexes take part in building, incubating eggs (about 30 days), and raising young, and the more aggressive individuals defend the nest. In southern California these kites group together in communities. They do not object to pairs of the same species building within 200 yards of their own nest, but the territorial boundaries are strictly observed. ... The normal egg clutch for Elanus is four, but varies from three to six.

 

 Food - Their diet is based largely on Microtine rodents. This is a large class of small rodents in the genus Microtus, generally known as voles. The most widespread vole in California is the California Vole, (Microtus californicus). Microtine rodents can have explosive population cycles. They can range from the density of 15,000 voles per hectare to 1 vole per hectare in just a few years. Frances Hamerstrom discusses a four year population cycle for the vole where in four years it goes from a high density of voles to an almost absence of voles.

 

From, Birds of Prey of the World p. 209

As in other species of Elanus, food includes small mammals (field mice, wood rats, pocket gophers, ground squirrels, shrews), reptiles, amphibians, and insects. They show a decided preference for living in the vicinity of fresh-water marshes and streams where food is readily available all through the year, and probably do not wander far, even in winter.

From The Birder's Handbook; p. 222

Diet: Especially California vole and other rodents, also birds, snakes, lizards, frogs, and large insects.

 

Hunting

From, Birds of Prey of the World p. 209 -

In the New World the White-tailed Kite often soars at a height of 60 or 70 feet while looking for prey on the ground. Remaining poised for half a minute at a time the bird then drops downward in an extended parachute maneuver to make the kill. Often it indulges in a pretty fluttering flight with quick wing beats. The display flight used in the nesting territory is a slow beating of the air with short strokes, the wings held at a sharp angle above the back, and the legs dangling.

 From Atlas of the Breeding Birds of Monterey County, California (1993) p. 88

The occurrence of the White-tailed Kite is closely related to the presence of voles and mice, and when the prey is depleted kites depart that area. Numbers and range seem to expand and contract in broad cycles, possibly tied to the abundance of its favored prey, the California Vole. For this reason the population is apparently cyclical in numbers, and breeding distribution may always be sporadic and unpredictable.

From Shuford, David W. (1993). Marin County Breeding Bird Atlas. p. 133-135

 

Because Kites tend to be nomadic and to decrease or increase rapidly with fluctuating vole populations, future atlasers should be very cautious in interpreting any changes they detect when they repeat the Marin atlas at a later date.

Habitat

From California Birds - Their Status and Distribution

Open, cultivated and marshy bottomlands with scattered tall trees; savannah; grassy foothill slopes interspersed with oaks; agricultural areas with trees for windbreaks; orchards; and roadside verges (for hunting). They are found mainly in the Upper Sonoran Life Zone below 2000 feet, but wanderers occasionally occur in the mountains.

From The Birder's Handbook p. 222

Breeding Habitat: Savanna, riparian woodland, marsh, partially cleared or cultivated fields, grassy foothills.

 

From Grinnell - (1944) The Distribution of the Birds of California.

 

Habitat: Of two sorts: low rolling foothills or valley margins grown scatteringly to valley or live oaks; and river bottomlands or marshes adjacent to, or inclusive of, broken or scattering deciduous woodland. An essential combination of conditions seems to be open grasslands, meadows or marshes for foraging, primarily for meadow mice, and near-by isolated dense-topped trees for perching and nesting.

Distribution:

From California Birds - Their Status and Distribution

Uncommon to locally fairly common resident. Although it is probably not truly migratory, the population scatters widely during the non-breeding season. Until recently winter roosts of more than 100 concentrated the population in localities from the Sacramento Valley and San Francisco Bay area south to San Diego County. Most out-of-range wanderers appear during fall, winter and spring.

From, Birds of Prey of the World p. 209

The North American population has not been numerous in historic times and long ago disappeared from the southern part of the United States, except in Texas and California, west of the desert from the upper Sacramento Valley to the San Diego area. By 1900 the White-tailed Kite was considered rare in California and was protected by state law. Its beautifully marked eggs, some with a cap of brown coloring at one end, are prized by oologists. Part of the survival problem of this evidently dying species, like that of the Swallow-tailed Kite, has been interference by humans.

Small, Arnold California Birds - Their Status and Distribution

Note: In recent years there had been an encouraging upsurge in the California population of these kites (which leveled off in the mid-1970s). This increase was probably due to an increase in the microtine rodent population as the result of new water projects, increased irrigation and the spread of agriculture. However, there was a steady and steep decline in coastal and near coastal southern California populations during the 1980s. Once the population leveled off, sharp local population fluctuations occurred, reflecting perhaps the cyclical situation in local rodent population. In some areas, the upswing in White-tailed Kites also indicated a reduction of local native floras and faunas due to conversion of indigenous vegetation to agriculture, and the expansion of conditions favoring both mice and kites. However, during the 1980s, the rapid urbanization of southern California and west-central California encroached upon agricultural lands, and may explain the movement of some kites to peripheral and marginal habitats (as into the fringes of the deserts), and the precipitous decline in areas where during the 1960s and 1970s they were fairly common. In some agricultural areas of the interior valleys, where kite populations were increasing during the 1960s and 1970s, conversion of crops favorable to microtine rodents resulted in unsuitable plantings of cotton, grapes and fruit orchards. Additionally, windbreaks, which served as nesting trees for the kites, were diminished.

From The Birder's Handbook p. 222

Winters within US. North American range greatly expanded since 1960; probably only raptor to have benefited from agricultural expansion. Aided by high adaptability to habitat disruption and increased abundance of rodents.

From Atlas of the Breeding Birds of Monterey County, California (1993) p. 88

Once considered endangered in California, the White-tailed Kite has made a great comeback in the state, being the only raptor to benefit from the spread of agriculture and the concurrent population explosion of its favored prey.

 


Chapter 2 - Historical Account of the White-tailed Kite

Appendices

Lesson Plans
Top
Avian Conservation Glossary


Florence Merriam Bailey - (1902) Handbook of Birds of the Western United States

 

Distribution: Tropical America, except the West Indies; north in the United States to about the latitude of San Francisco on the Pacific coast, St. Louis in the interior, and South Carolina in the east.

The kites are resident in the oak groves of Santa Clara Valley, and frequent the marshes about San Francisco Bay, where Mr. W. K. Fisher has found them catching large numbers of the California meadow mouse.

 

Grinnell - (1915) A Distributional List of the Birds of California

It used to be particularly numerous around San Francisco Bay; but it is now everywhere very much reduced in numbers and restricted in range, with promise of an early extinction.

Dawson - (1923) Birds of California, Volume 3, p. 1649

Recent ornithological literature bristles with records of occurances of the White-tailed Kite, once upon the verge of extinction, but, now, it is believed, being slowly nursed back into life. The cause of the near tragedy, now hopefully averted, was expressed several years ago by Dr. Grinnell: "With no doubt whatever, the present rarity of this hawk in California is due to the associational preference for marshes, where its habit of flying slowly back and forth at a moderate height above the ground in the lookout for meadow mice and insects makes it an easy target for the thoughtless hunter. In my experience the average sportsman is still unenlightened enough to shoot down any sort of 'hawk' that flies his way, provided game is not at the moment expected." Yet this is the bird of which Cooper (following Heermann) could write in the Sixties: "This beautful and harmless species is quite abundant in the middle districts of California, remaining in large numbers during winter among the extensive tule marshes of the Sacramento and other valleys."

Hoffman - (1927) Birds of the Pacific States p. 64

There are probably not more than fifty pairs left in California and in spite of protection by law the number is slowly decreasing.

 

Grosvenor, National Geographic Society's The Book of Birds - 1939

It is found over tree-dotted prairies and savannas, marshes, and semi-open valleys. Though fifty years ago it was common, it has decreased steadily until now it is to be classed among our unusual birds. Despite the fact that it has been afforded protection in recent years, the species does not seem able to increase.

The White-tailed Kite is found in California from the upper Sacramento Valley and Humboldt County, south to northern Baja California and from Texas, Oklahoma, and Florida to Guatemala.

 

Grinnell - (1944) The Distribution of the Birds of California.

Resident throughout year within metropolis of range; but shifts about locally, both seasonally and from year to year, in accordance with food supply. Formerly, prior to about 1895, common and widespread in valley and lower foothill territory, but now rare or entirely gone from many sections. A slight trend toward recovery, in area and numbers, is latterly in evidence.

 

 

A. C. Bent , Life Histories of North American Birds

This gentle and attractive bird seems to have become exceedingly rare, or to have been entirely extirpated, in the eastern portions of its North American range. During my six seasons, or parts of seasons, spent in various portions of Florida I have never seen this kite; once a special trip was made to a section where our guide said they had recently nested, but no sign of them was found. Donald J. Nicholson tells me that he has not seen one there since 1910. We could not find it in southern Texas, and I have no recent records of it there. In certain sections of California it seems to be holding its own, though exceedingly local in its distribution, and nowhere universally abundant. I doubt if it ever was very abundant, although Cooper (1870) referred to it as "quite abundant in the middle districts of California, remaining in large numbers during winter among the extensive tule marshes of the Sacramento and other valleys", and Belding (1890) considered it "still a common resident" about these marshes "in the centre of the State." But Belding quotes Dr. B. W. Evermann, as calling it "a rare resident" in Ventura County, as early as 1886; and he quotes W. E. Bryant as saying that "it is still a very rare resident" in Alameda County. It seemed to be the general opinion, at that time, that the white-tailed kite was a disappearing species. As a result, it has since been rigidly protected by law and exempted from collecting permits.

"Now comes more recent light on the subject, which is more encouraging. Dr. Gayle B. Pickwell (1930) has published the results of his exhaustive study of the literature and his field work in the Santa Clara Valley. Referring to past and present conditions in that region, he says:

"In spite of the fact that Taylor, in 1889, wrote of the Kite, "I venture to assert that there are not more than four pairs this year breeding within a radius of seven miles of that city (San Jose)", today, forty-one years later, there are still that many or more.

Let us estimate that an average of four pairs of Kites (too high an estimate for some, too low, perhaps, for others) frequents each. We have then sixteen pairs of Kites in this entire valley. Twenty pairs, forty birds, I feel convinced, account for every Kite from Gilroy to the Bay and from Mount Hamilton to the summit of the Santa Cruz Mountains.

The Kite was certainly more numerous In San Joaquin and Sacramento counties forty to sixty years ago than it is now. In other regions where it was present, especially in marsh districts, undoubtedly It has been seriously reduced In numbers. The condition in hill sections inhabited by it can be but guessed at. Here it probably has suffered least.

This Kite is probably a dying species, never within historical times having predominated as such raptorial birds as the Desert Sparrow Hawk or Red-tailed Hawk for instance.

Since the above was written Dr. Pickwell (1932) has published a "requiem" for the kites in this valley; whereas he estimated that there were possibly 16 to 20 of these kites in the Santa Clara Valley in 1928, he now says: "This day (October 30, 1931) there cannot be more than two or three, and all too possibly none." We hope that this is a mere local condition.

His observations on the home life of these kites were made in the foothills of the Mount Hamilton Range in Santa Clara County:

The Slatore ranch lies in the foothills whose summits are grass-covered with wild oats and bromes, with scattered valley oaks and live oaks, and here and there a cluster of California coffee berry (Rhamnus catiforaica) and gnarled Sambucus. Rocky outcrops, where more moisture may be trapped, have curious copses of scrubby growths of toyon, holly-leaved cherry, sages and sage brush; and the gullies lined with buckeye, California laurel, and poison oak run down to Silver Creek where the laurels and willows predominate. But the hills are mostly smooth as velvet, golden velvet most of the year, and green oaks are scattered over the velvet, like buttons on a buxom vest. In three buttons on this velvet vest were occupied nests of the White-tailed Kite.

That such a habitat is not an unusual Kite home is shown by the fact that all the Kites of Santa Clara Valley today are, excepting one or two pairs, restricted to the lower foothills of the Mount Hamilton Range and Santa Cruz Mountains, on either side of the north end of the Valley. The exception is of not more than two pairs that occur to the north of San Jose between that city and the Alviso salt marshes. These frequent the cottonwoods and eucalyptus trees of the Coyote Creek and, not infrequently, are seen hunting over the treeless marshes at the foot of the Bay in common with Marsh Hawks, native there, and Turkey Vultures and Red-tailed Hawks from the hills.

Bendire (1892) says of their haunts: "Their usual resorts during the breeding season are the banks of streams or the fresh water marshes, especially if a few scattered live oaks or willow groves are close by, and their favorite nesting sites are the tops of live oaks, although other trees are also made use of whose foliage securely conceals the nest during incubation."

The impression I gained from men I talked with in California and from my own limited experience there was that this kite shows a decided preference for the vicinity of water, fresh-water marshes and streams; in such places it finds its food readily available all through the year, and it probably does not wander far away even in winter. According to Audubon (1840) it was found in similar haunts in Texas and Florida.

Ludlow Griscom Audubon's Birds of America (1950)  

A rare and beautiful hawk now almost extinct in the Southeast, a few in Texas and California. Reapears in South America.

From Atlas of the Breeding Birds of Monterey County, California (1993) p. 88  

Historical Occurrence

The overall distribution has dramatically changed over the past century. The increase in voles with the cutting of forests for agriculture has benefited this species. Once considered so rare that it was one of only five species fully protected under California law (along with the California Condor, Bald Eagle, Peregrine Falcon, and Trumpeter Swan; Fish & Game Code), the species has greatly expanded throughout the southern United States since 1960. In Monterey County kites were known from the Carmel Valley for years but the occurrence in the upper Salinas Valley is recent. No birds were recorded there by Willett (1908) but one bird was noted along the Nacimiento River on Camp Roberts by Mowbray (1947). Likewise, the spread to the Big Sur coast is recent, as the species was not seen by Jenkins (1906) or Pemberton & Carriger (1915). At Hastings Reservation, in the upper Carmel watershed, habitat is marginal for this species and kites occurred in only 17 of the 43 years between 1938-1980 and nested in only five of those years.

From Shuford, David W. (1993). Marin County Breeding Bird Atlas. p. 133-135

Early declines were apparently caused by shooting, habitat loss, and perhaps by overzealous egg collectors. The eggs were highly prized because of their scarcity, because of the variability between egg sets, and because Black-shouldered Kite eggs are among the most beautiful of those of all North American birds. Illegal egg collecting continued until at least 1940 despite laws passed in 1905 to protect the birds and their nests (Williams 1940); further protection was afforded by legislation in 1957. California's Kite population has apparently increased because of the birds' ability to tolerate habitat fragmentation caused by agricultural practices, to exploit increased Microtus populations thriving in fields irrigated year round, and to reproduce at a high rate. A clutch size of four to five eggs and the ability to double brood in a single year are both unusual adaptations for a hawk ... Martin (1989) noted that the amount of irrigated agricultural land in California increased by 42% from 1944 to 1978, coinciding with the period of dramatically increasing Kite numbers.

The great year-to-year fluctuations in Kite numbers appear, at least in part, to be tied to similar changes in the prey base influenced by rainfall. Pruett-Jones et al. (1980) found a significant positive correlation between Kite numbers and rainfall. This perhaps is explained by the fact that microtene rodents need standing water to reproduce ... and that their numbers are usually reduced in a drought. The decline in Kite numbers in California during the 1975-76 to 1976-77 drought and the substantial increase in numbers in Oregon at that time, including their first breeding record ... further suggests a link between rainfall, vole populations, and Kite populations.


Chapter 3 - The Christmas Bird Count Records

Appendices

Lesson Plans
Top
Avian Conservation Glossary


Christmas Bird Counts began in 1890 as a reaction by Chandler Robbins and friends to the wholesale slaughter of many of the nation's birds. Over the past 100 years private citizens have ventured out into their neighborhoods to conduct a census of wintering birds during the last two weeks of the year. In 2008 there were 2,111 Counts that totaled 57,700,668 birds.

A Christmas Bird Count is done by volunteers who break into teams and canvas a selected segment of a circle whose diameter is 15 miles long which equals 176 square miles and approximately 112,000 acres. The territory is a circle strategically drawn over a prime birding area. The circle is carefully segmented and teams are assigned. Some of the teams start before dusk and bird past 5 pm so they can hear owls and add them to the count record. Each count has a compiler and every compiler has a rare bird committee made up of seasoned experts to deal with occurrences of unusual birds. Efforts are made to keep the records as reliable as possible. The participants count every bird. If a flock of birds is seen then the number is estimated as best as possible. In the case of hawks and owls and other larger birds efforts are made not to count the same bird twice. Teams will communicate with adjacent teams to check notes to make sure that the bird didn't fly over into their territory.

I had a professor at San Jose State who told me that Christmas Bird Count data was worthless data. I don't agree with him. Perhaps one count by itself doesn't signify very much, but when you have over 100 years of CBCs (Christmas Bird Counts) and the citizen scientists who participate are as well skilled as they are, then the data is valuable; the trends significant.

The White-tailed Kite is easy to identify in the field. There are very few birds that can be confused with it. By its nature it stays out in the open where it can easily be seen. The problem is counting the bird twice, or three times as the bird wanders around to different areas that are being counted by different groups.

From the USGS Avian Conservation Glossary: "Index method - a counting method involving sampling that yields measures of relative abundance rather than density values." Is the CBC a determinant of relative abundance or density values? Density is determined for a circle but no effort is made to extrapolate to the whole area.

Landscape index: index of landscape structure (pattern), including richness, evenness, patchiness, diversity, dominance, contagion, edges, fractal dimension, nearest neighbor probability, and the size and distribution of patches.

 

Table 1
California Christmas Counts Reporting White-tailed Kites (including Black-shouldered Kite) Between 1900 and 2004
Count Year
# of Birds
# of Counts with Kites
Count Year
# of Birds
# of Counts with Kites
Count Year
# of Birds
# of Counts with Kites
Count Year
# of Birds
# of Counts with Kites
1900 - 1917
0
0
1948
12
5
1968
326
16
1988
1313
61
1918
1
1
1949
3
3
1969
359
30
1989
1231
63
1919-1929
0
0
1950
8
5
1970
439
30
1990
1120
58
1930
1
1
1951
8
5
1971
620
27
1991
1188
58
1931
5
2
1952
41
9
1972
637
31
1992
1068
60
1932-33
0
0
1953
42
10
1973
604
34
1993
1195
58
1934
3
1
1954
79
10
1974
669
33
1994
1196
67
1935
2
2
1955
67
8
1975
875
40
1995
1794
72
1936
1
1
1956
36
9
1976
1436
48
1996
1318
71
1937
8
3
1957
64
11
1977
1275
48
1997
1419
73
1938
3
2
1958
73
10
1978
952
49
1998
1502
70
1939
3
2
1959
67
11
1979
799
45
1999
1368
65
1940
2
2
1960
118
17
1980
1187
56
2000
1966
82
1941
3
2
1961
81
14
1981
1807
69
2001
1950
71
1942
4
1
1962
154
16
1982
1425
64
2002
1666
71
1943
0
0
1963
125
16
1983
1484
65
2003
1385
75
1944
6
3
1964
225
14
1984
2230
66
2004
2046
70
1945
1
1
1965
232
22
1985
1940
74
2005
1785
80
1946
2
2
1966
336
16
1986
1339
64
2006
1623
80
1947
13
6
1967
311
21
1987
1395
66
2007
1991
84

Table 2 
1971 California Christmas Bird Count with observations of at least one White-tailed Kite

NC = No Count

Auburn
NC
Los Angeles
0
Pasadena
4
Anza Borrego
NC
Long Beach
NC
Peace Valley
NC
Angwin
1
Lake Henshaw
NC
Red Bluff
NC
Ano Nuevo
NC
Lost Lake
1
Redding
NC
Arcata
NC
Lancaster
NC
Redlands
0
Bakersfield
NC
Lone Pine
NC
Rancho Santa Fe
NC
Big Bear Lake
0
Lake Almanor
NC
Santa Ana River Valley
NC
Benicia
106
Los Banos
20
Santa Barbara
26
Bear Valley
NC
La Purisima
NC
San Diego
13
Big Sur
NC
LaGrange
NC
San Francisco
NC
Bishop
NC
Marin County
39
Santa Maria
NC
Butterbredt Springs
NC
Moss Landing
25
Salton Sea North
0
Calaveras
NC
Milburn
NC
Santa Catalina
NC
Centerville Beach
34
Mount Hamilton
NC
San Jose
57
Contra Costa County
23
Mineral
NC
South Fork Valley
NC
Clear Lake
NC
Mojave River Valley
NC
San Jacinto Lake
NC
Claremont
NC
Mono Lake
NC
Sacramento
140
Chico
1
Mendocino
NC
Sonora
NC
China Lake
0
Modoc
NC
San Bernardino
0
Carrizo Plains
0
Monterey
0
Springville
NC
Crystal Springs
3
Moro Bay
1
Santa Rosa
36
Caswell
NC
Mount Shasta
NC
Salton Sea South
0
Death Valley
NC
Malibu
0
Stockton
39
Escondido
NC
Morongo Valley
NC
San Juan Capistrano
NC
Etna
NC
Oakland
1
San Fernando Valley
0
Folsom
NC
Orange County
27
Sierra Valley
NC
Falls River Mills
NC
Orange County (Northeast)
12
Tehachapi
NC
Grass Mountain
NC
Oroville
1
Tule Lake
NC
Grass Valley
NC
Oceanside
7
Thousand Oaks
NC
Hayward
34
Palo Alto
22
Truckee
NC
Honey Lake
0
Panoche Valley
NC
Ukiah
NC
Hollister
0
Putah Creek
NC
Ventura
NC
Idyllwild
0
Pinnacles
NC
Willow Creek
NC
Joshua Tree
0
Parkfield
NC
Western Sonoma County
0
Kern River Valley
NC
Palos Verdes
1
Yosemite
0
Lewiston
0
Point Reyes
12
Yreka
NC

Table 3
1997 California Christmas Bird Count with observations of at least one White-tailed Kite

Auburn

44

Los Banos

82

Rancho Santa Fe

15

Angwin

4

La Purisima

11

Santa Ana River Valley

2

Ano Nuevo

55

La Grange

17

Santa Barbara

43

Arcata

8

Marin County

28

San Diego

17

Bakersfield

1

Moss Landing

30

San Francisco

2

Benicia

118

Milburn

2

Santa Maria

27

Bishop

1

Mendocino

16

San Jose

19

Centerville Beach

24

Monterey

3

South Fork Valley

1

Contra Costa County

26

Moro Bay

34

San Jacinto Lake

40

Clear Lake

7

Malibu

8

Sacramento

63

Claremont

9

Oakland

11

San Bernardino

7

Chico

5

Orange County

56

Springville

8

Carrizo Plains

3

Orange County (Northeast)

29

Santa Rosa

41

Crystal Springs

3

Oroville

8

Salton Sea South

5

Caswell

26

Oceanside

31

Stockton

49

Escondido

24

Palo Alto

26

San Juan Capistrano

14

Folsom

59

Putah Creek

7

San Fernando

2

Hayward

38

Pinnacles

1

Tule Lake

1

Hollister

20

Parkfield

1

Thousand Oaks

32

Kern River Valley

1

Palos Verdes

5

Ukiah

16

Los Angeles

8

Point Reyes

43

Ventura

16

Long Beach

2

Padadena

5

Willow Creek

1

Lake Henshaw

2

Peace Valley

23

Western Sonoma County

7

Lost Lake

7

Red Bluff

14

73 counts, 1425 Birds identified

Average per count = 20

Lancaster

2

Redlands

3

 


 

Chapter 4 - Similar Species

Appendices

Lesson Plans
Top
Avian Conservation Glossary

 


The Northern Harrier is similar to the White-tailed Kite in many ways. They share very similar habitats. In practically every Christmas Bird Count that had a White-tailed Kite, there was also a Northern Harrier. There are more Northern Harriers than White-tailed Kite and they are found in more counts than White-tailed Kites. The harrier's diet is heavily dependent on microtine rodents. Both species hunt in very similar ways. While approximately 80% of the kite's population is found in California the Harrier's population is spread out through many states. The Northern Harrier has a migratory population in the states and a resident population that does not migrate. While the White-tailed Kite's diet is 99% California Voles, the Northern Harrier's diet is 56% California Voles.

The Red-tailed Hawk represents a raptor that is also a generalist and also has both a migratory and a resident population.

 

Table 4 - Comparison of White-tailed Kite and Northern Harrier Population for the United States Between 1981 and 2004

(Utilizing Christmas Bird Count Data)

White-tailed Kites
Northern Harriers

Number of Birds
Number of Counts
Number of Birds
Number of Counts

1981

2031
92
11028
663

1982

1666
89
11111
794

1983

1818
94
10218
778

1984

2457
96
11284
808

1985

2119
102
11699
836

1986

1769
99
11008
845

1987

1848
104
10920
966

1988

1896
102
11162
856

1989

1685
109
13155
907

1990

1356
88
11746
922

1991

1499
91
12184
938

1992

1516
102
11780
950

1993

1789
103
11407
908

1994

1627
109
12348
963

1995

2231
118
15926
1012

1996

1640
111
13119
931

1997

1784
112
12763
922

1998

1915
107
13612
960

1999

1797
111
15563
1048

2000

2388
126
16689
1134

2001

2343
127
15480
1050

2002

2174
121
13955
1103

2003

1783
119
12925
1095

2004

2418
112
15119
1094


Chapter 5 - The California Vole

Appendices

Lesson Plans
Top
Avian Conservation Glossary


From Wikipedia: A vole is a small rodent resembling a mouse but with a stouter body, a shorter hairy tail, a slightly rounder head, and smaller ears and eyes. There are approximately 70 species of voles; they are sometimes known as meadow mice or field mice in America. The voles, together with the lemmings and the muskrats, form the subfamily Arvicolinae.

Species of voles can be found in Europe, Asia, North Africa and North America, and tundra areas.

Depending on the species, the vole's diet consists of seeds, tubers, conifers needles, bark, various green vegetation such as grass and clover, and insects.

Many carnivores such as wolves, owls, hawks, coyotes, foxes, weasels and cats ( i.e. Angus) eat voles. A common predator to voles is the short-eared owl.

The average life of a vole is 3–6 months. Voles rarely live longer than 12 months. The longest lifespan of a vole ever recorded was 18 months.

Reproductive Rate - predators breed at a linear rate. Voles breed at a geometric rate. Vole's population seems to be controlled by periodic crashes. Cause of crashes is not well known.

How many species of voles are there in the United States? How many species of microtus are there in the United States?

Animal Diversity Web University of Michigan Museum of Zoology

"Habitat - California voles inhabit areas of broad-leaved chaparral, oak woodlands, and grasslands along the Pacific Coast in northern Baja California to central Oregon. This species has a restricted distribution, which is possibly due to relic populations. It seems to utilize unusual habitats in California compared to other species of voles throughout the North American continent. Marshy ground, saltwater and freshwater locations, wet meadows, coastal wetlands and dry, grassy hillsides are the preferred macrohabitats of this species.

"Ovulation in M. californicus is induced by copulation. This species experiences a post-partum estrus, and breeding can occur within fifteen hours after young are born. This allows up to 4 or 5 litters a season"

 Voles can breed every three weeks under good conditions.

The breeding season seems to heavily rely on the wet season in non-coastal parts of California. In coastal populations breeding is aseasonal.

Number of offspring is 1 to 11; average of 4 or 5.

Gestation period is 22 days.

Time of weaning is 2 weeks.

Time to independence is 2 weeks.

Age at sexual or reproductive maturity (female) is 21 days.

Age at sexual or reproductive maturity (male) is 25 to 42 days.

"There are a great number of vole predators, including coyotes, kestrels, hawks, weasels, kits, owls, snakes, herons, egrets, and feral cats. Because of their rapid reproduction and periody high population densities, these voles are a keystone prey species."

From Michael H. Ferkin: (http://biology.memphis.edu/ferkin.htm) "Microtene rodents are best known for their unique population dynamics that include spectacular increases in population density (more than 15,000 voles/hectare) followed by equally remarkable 'crashes' (less than 1 vole/hectare). Although the causes of microtene population fluctuations remain hidden, many researchers stress the importance of behavioral interactions as a mechanism that regulates vole demography. It has been hypothesized that seasonal plasticity of behavior and reproduction among individuals profoundly affect microtene social organization and demography. My approach to the study of animal behavior includes both proximate and ultimate levels of analysis."

 


  

Chapter 6 - Population Ecology

Appendices

Lesson Plans
Top
Avian Conservation Glossary


Population ecology is the study of the reasons why the numbers of an animal species goes up and down. What are the factors that cause populations to fluctuate? Farley Mowet, in his book Never Cry Wolf, retells an Eskimo myth that explains the relationship between the wolf and the caribou; between predator and prey.

Initially the caribou lived in an environment without the wolves and the caribou thrived. They ate well and prospered. But soon their numbers were too great for their food supply. They started to starve and the population suffered as the weak caribou reproduced. So the wolf was brought into their land. The wolf preyed upon the weakest of the caribou. Eventually the caribou became strong again because the wolf takes out the weakest of the herd and only the strong survive and only the strong reproduce.

In a perfect situation each species of animal has an intrinsic rate of natural increase. This increase would continue until the population was at the point where it could be supported by the available resources. The small letter "r" is used to represent the rate of population increase and the letter "k" is used to represent the point where the population can be supported by the available resources.

Of course the relation between predator and prey is more complicated than the Eskimo story. There are fluctuations in the resources. There are fluctuations that occur to the prey items. There are fluctuations that occur to the predators. There are fluctuations that occur to the weather that affect the food that affects the prey items that affects the predators.

Studying the population ecology of the White-tailed Kite is a process of identifying the factors involved in a sustainable population. A sustainable population for one species is not necessarily sustainable for another species. It was realized after the Passenger Pigeon became extinct, that their natural history required that they maintain a very large population; a population so large that it came into conflict with the growing nation of America.

The White-tailed Kite is a microtene obligate. The main prey item for the White-tailed Kite is the vole; a microtine mammal. Part of the population ecology of the vole is that its population numbers are very erratic. In a good year they can have an incredible density of 15,000 voles per hectare. Within a year or two this density can shrink to one vole per hectare when the food and the water become scarce. The challenge for the White-tailed Kite is to be able to successfully respond to these changes.

Population ecology also includes the effect of one species on another species. This includes the human animal species. Many historical accounts talk of the ease which indiscriminate hunters were able to shoot the White-tailed Kite.

 

From Odum's Fundamentals of Ecology: p. 239

Prior to 1907 there were estimated to be about 4,000 deer and a good population of predators - pumas and wolves - on the Kaibab plateau, an area of about 700,000 acres on the north side of the Grand Canyon of Arizona. Between 1907 and 1923 a concerted effort was made to remove the predators. By 1925 the deer population had increased to 100,000 which was far beyond the carrying capacity of the vegetation. Everything in reach - grass, tree seedlings, shrubs - was eaten and the whole area gave the appearance of a huge over-grazed and over-browsed pasture. In two winters 40 per cent of the enormous herd starved to death, and decline continued to about 10,000. The range continues to be depleted, and damage to forest reproduction will be evident for a long time. It has been estimated that the original range could have supported no more than 30,000 deer. Thus, the predator-prey interaction was maintaining a relatively stable equilibrium, with the deep population being held well below the point where its own food supply would be depleted.

One of the goals of population ecology is to understand any patterns that could exist in nature that would help explain the ecology of particular species.

To do science is to search for repeated patterns, not simply to accumulate facts, and to do the science of geographical ecology is to search for patterns of plant and animal life that can be put on a map.

Robert MacArthur, Geographical Ecology


Chapter 7 - Some Notes on Hunting

Appendices

Lesson Plans
Top
Avian Conservation Glossary


Much evidence points to hunters being the cause of the kite's brush with extinction. Between 1880 and 1930 it seems very possible that an effort was made to exterminate all predators. The White-tailed Kite was an easy, convenient target given its white plumage, and its tendency to hover low over the fields.

There is a complicated history/relationship between ornithology and hunting. It is not the simple relationship that many people might expect. It is necessary, initially, to indicate that the discussion about hunting includes only legal hunting. There are people who do not purchase licenses, and there are people who kill animals that they know they shouldn't kill. They are an embarrassment to the hunting community at large.

There are also birdwatchers that hate all hunters and consider the whole process of hunting repellent. But they are eager to go on field trips to refuges that are bought and maintained by the fees paid by hunters. In California much of the land that sustains the large wintering populations of ducks, geese, other waterbirds, and hawks, is paid for from the fees collected from hunters. It has been suggested that hunters have bought a lot more strategic land than have birdwatchers.

This is not to say that there have not been egregious examples of ruthless, damaging hunting. In the 19th century the market hunters devised methods of slaughtering Passenger Pigeons so that they killed an estimated 10 billion birds in a period of a few years. It is miraculous that many species of shorebirds did not also become extinct since they were also the target of market hunters.

Additionally, there was a period of time when people had a mistaken notion of community ecology. People determined that predators were bad animals to have around because they killed songbirds, livestock, pets, etc., and because of this they should be destroyed.

One of the classic studies of the effect of the effort to kill all predators took place in Kern County, California around 1927. The whole community organized to kill as many predators as possible. So many predators were killed so quickly that the rodent population skyrocketed and that had a very dire effect on all aspects of life. At one point there were so many rodents on the roads being run over by cars, that cars were having problems staying on the roads because the roads became slippery due to the number of dead rodents.

Hunting still represents the wild-west independent nature of the United States. There is a culture of hunting that is not very old. In the life history accounts found in A. C. Bent's Life Histories of North American Birds it is possible to find candid comments by hunters who are the ornithologists and comments from them about the hunters who are not ornithologists.

There was still the concept that the resources were infinite. They did not have to worry about how many animals were shot because there would always be replacement resources. Extinction was not understood. The Passenger Pigeon and the Carolina Parakeet were exceptions not the rule.

Between the Kaibab Peninsula's deer population and Kern County anti-predator campaign it seems that the citizens did not understand the prey/predator relationship so classically outlined in the Eskimo myth.

 


Part 2 - The Lesson Plans

Bibliography

Appendices

Lesson Plans

Table of Contents

The purpose of the lesson plans is to provide students an opportunity to do real research about a current situation.

These lesson plans are dynamic because the questions that they ask are mostly research challenges as opposed to figuring out right and wrong answers.

These lesson plans are also unique because they utilize the Internet to provide data to work with; data that previously would have taken hours to gather.

One of the goals is to utilize life sciences and student initiative to do this research.

The study of birds has consistently been regarded as a hobby but not a science. Ian Newton in his book Population Ecology of Raptors notes that the life histories of birds of prey are seldom used as examples in the studies of prey/predator relations and population ecology in general. The study of a population of animals is a scientific study.

Examination of a predator whose main niche is to prey upon rodents whose numbers can explode and cause health problems to the community is a serious consideration.

Work done by students can be sent to birdcentral.net and posted.

Caution: Between the years 1960 and 1980 the White-tailed Kite had its name changed to the Black-shouldered Kite. If you try to gather data from the Audubon CBC database for any portion of years between 1960 and 1980 you will need to use the name Black-shouldered Kite instead of White-tailed Kite.


 Lesson Plans

1. How many voles

5. Graphing the results

9. History of California Agriculture

2. The Real Estate Question

6. Population Dynamics

10. Sim City meets the White-tailed Kite

3. Develop a scenario

7. Double or Nothing

11. White-tailed Kite as an Indicator Species

4. Average, Mean, Mode

8. Profile of a Christmas Bird Count

12. Microtene Bust

 


1. How many Voles?

Bibliography
Appendices
Table of Contents

Lesson Plan Name

How many Voles?

Subject Area

Zoology

Topic Area

Life Science

Grade Level

6 -12

Objectives

To use mathematics to help determine food web parameters

Standards

Materials

Calculator

Instructional Procedure

During the months between October and March much of California is inhabited by hawks that have left the far north to be in a more temperate climate and more importantly, to be where there are more prey animals available.

What you need to do is to use the number of predatory birds to determine an estimate on how many California Voles there might be in the area. If X number of birds spend 180 days in a definable territory then we can assume that they are finding food to keep them alive.

Activities

Select a Christmas Bird Count (CBC) that has a good diversity of birds that share the same diet as the White-tailed Kite. A table (Appendix H) has been provided that identifies a group of birds that share similar diets.

For this study we have determined that the ready-to-eat vole weighs 25 grams. Pick a CBC that has a number of vole predators. Set up a formula and determine how many voles theoretically would be eaten to support this number of birds for a winter period.

Resources

Use Appendix H for energetic requirements of selected hawks and owls.

Audubon Christmas Bird Count Historical Database

Additional Questions

1. What other species in the CBC eats Microtus species?

2. Dunk reports that there needs to be a certain availability of voles to make hunting successful. He suggests 1500 voles per territory and that an average territory is 10 hectares.

3. Obviously this is a pretty narrow scenario. Many variables are not included. List some of the major variables that would need to be considered to make this a more accurate study of wintering food needs.

4. Take ten similar counts and run the same equation. Are there any similarities in the numbers?


2. The Real-Estate Question

Bibliography

Appendices
Lesson Plans
Table of Contents


Lesson Plan Name

The size of the territory

Subject Area

Zoology

Topic Area

Life Science

Grade Level

6 -12

Objectives

To learn more about how different species utilize the land.

To understand the logistics of a life cycle.

Standards

Materials

Calculator

Instructional Procedure

How much territory does a kite need to breed? If there are 140 birds, 70 pairs, in 150 square miles, how many of those pairs can breed? What are the factors that are involved with this question?

Activities

1. From the Appendix A pick a count that has an appropriate number of kites.

2. For this question we will assume that the number of wintering kites will be the number of breeding kites.

3. Translate the CBC area into hectares (See Appendix G)

4. Given a breeding area of 10 hectares how many breeding territories could there be in this area?

Resources

Audubon Christmas Bird Count Historical Database

3. Scenarios

Bibliography
Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

Develop a Scenario

Subject Area

Science

Topic Area

Life Sciences

Grade Level

8 - 12

Objectives

To interpret the meaning of a bird census.

Standards

Materials

Instructional Procedure

Here is an opportunity to become a reporter/mystery writer, manager. The CBCs are filled with many numbers but what those numbers tell us is up to us to find out. The challenge here is to take a series of counts and develop an explanation of what you think the numbers mean. How you do this is very much up to you. You may compare a number of different counts. You may want to take a ten year period of one count that shows a wide range of numbers. Your job is to develop a scenario for what you pick that helps to explain what the numbers mean.

Activities

Identify a sub-set of counts.

Graph the numbers that you use and develop a scenario that suggests what the graphs might mean.

Find some outside resources that pertain to your set of numbers that helps to explain them more fully.

Resources

Audubon Christmas Bird Count Historical Database

4. Average, Mean, Mode

Bibliography
Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

Average, Mean, median

Subject Area

Mathematics/Science

Topic Area

Life Science

Grade Level

8 -12

Objectives

To connect statistical analysis with bird census data

Standards

Materials

Calculator

Instructional Procedure

The concepts of average, mean, and mode are used to express different aspects of a group of numbers. Through the use of these terms we can better understand the character of the data that has been gathered.

Activities

1. Select a CBC that has at least 20 different counts.

2. Determine the average, the mean, and the mode for each count.

3. Discuss what these three expressions tell you about the character of these counts.

4. Which one of the three terms is more appropriate for this count and why.

Resources

Audubon Christmas Bird Count Historical Database

5. Graphing

Bibliography

Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

Graphing

Subject Area

Mathematics/Science

Topic Area

Grade Level

6 - 12

Objectives

To introduce the concept that zoological results can be graphed

Standards

Materials

Graphing software

Instructional Procedure

Graphs provide an opportunity to visually identify the nature of a set of numbers. We can look at a series of numbers and get a sense of what is known but the numbers along with a graph can quite often show trends in the numbers more dramatically.

Activities

1. Pick a CBC with at least 20 years of results. (See Appendix A)

2. Graph the results and be sure to label the axes.

3. Interpret what the graph visually shows.

Resources

Audubon Christmas Bird Count Historical Database

6. Population Dynamics

Bibliography
Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

Population Dynamics of the California Vole

Subject Area

Zoology

Topic Area

Life Sciences

Grade Level

Grades 5 - 7

Objectives

To better understand the logistics of animal populations.

To better understand the prey/predator relationship.

Standards

Materials

A calculator

Instructional Procedure

The Prey-Predator relationship is sometimes a difficult concept for someone to understand who has been told to protect animals. But to understand the place of raptors in an environment we need to consider what would happen if they weren't present. By considering the ability of mice to reproduce with a quick turn around very dramatically communicates the necessity of predators.

Activities

The California Vole has a gestation period of 3 weeks. They have, on the average 6 to 10 babies. Those babies mature in about 5 weeks. That means they are now ready to have their own babies. Anticipate that there will be an equal percent of 50% male babies and 50% female babies. If you start on January 1 with a pair of voles and there are no predators or disease, approximately how many mice will you end up with by June 30; December 31?

If you start with a pair of voles on Jan. 1 theoretically when would you have 1500 voles?

Resources

Some birds who are very responsible for killing voles are: White tailed Kite, Barn Owl, Gt. Blue Heron, Common Crow.

 

7. Double or Nothing

Bibliography
Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

Double or Nothing

Subject Area

Zoology

Topic Area

Life Sciences/Math

Grade Level

Grades 3 - 6

Objectives

To understand the mathematical description of prey-predator relations.

To understand the difference between linear and geometric growth.

Standards

Materials

scratch paper

Instructional Procedure

This is another exercise that expresses how populations can grow when there aren't balancing factors. Students are offered the choice between being paid a lump sum of $100,000 for one month of work or being paid a penny a day but having the amount doubled every day for the month.

This exercise helps to demonstrate the difference between linear growth and geometric growth.

Activities

1. You are going to work for one month and your employer has given you the choice between getting paid $100,000 for the month or getting one penny a day. But that penny gets doubled every day for 31 days. So on day one you get .01 and on day two you get .02. The amount gets doubled every day for 31 days. It's your choice.

2. What does this have to do with the California Vole?

8. Profile of a CBC

Bibliography
Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

Profile of a CBC

Subject Area

Science

Topic Area

Life Science

Grade Level

9 - 12

Objectives

To understand the concept of ecology.

Standards

Materials

Instructional Procedure

We know the basic details of a Christmas Bird Count. It is a bird census that takes place on a particular day during the last two weeks of each year. The participants count and list all the birds found over a 24 hour period. The count takes place in a circle with a diameter of 15 miles.

Your profile will add to these details by including the other organisms involved from the human organisms to the domestic organisms to the wild non-bird organisms that don't get counted.

Activities

Pick one of the CBCs from the Audubon Historical Database that includes White-tailed Kites.

1. What industry is in the area?

2. What farms and ranches are currently working? How many farm animals?

3. Is there any hunting going on in the area on the same day?

4. How many domestic pets?

5. What has been the economic history of the area?

Resources

Google

9. History of California Agriculture

Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

History of California Agriculture

Subject Area

History

Topic Area

Grade Level

6 - 12

Objectives

To better understand the role of agriclture in the ecology of the state.

Standards

Materials

Instructional Procedure

Create a brief history of the major changes in California agriculture during the period from1880 to 1980.

Number of farms

Number of ranches

Irrigation access

Activities

Resources

10. Sim City Meets the White-tailed Kite

Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

Sim City Meets the White-tailed Kite - Defining K

Subject Area

Science

Topic Area

Life Science

Grade Level

8 - 12

Objectives

To better understand the dynamics of an animal community.

Standards

Materials

Instructional Procedure

Activities

You have suddenly acquired a management opportunity. You get to create your own maximum White-tailed kite environment. What would an ideal kite environment look like? 

In a short essay develop an ideal White-tailed Kite environment. Take into consideration what resources will be needed on a year round basis.

How many voles are there? How many other mammals? Where is the water coming from? What is the human involvement? How many wintering kites are there and how many breeding kites?

Resources

11. The White-tailed Kite as an Indicator Species

Bibliography

Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

The White-tailed Kite as an Indicator Species

Subject Area

Zoology

Topic Area

Life Science

Grade Level

9 - 12

Objectives

To understand what an Indicator Species indicates.

Standards

Materials

Instructional Procedure

The White-tailed Kite has very specific geographical needs and prey requirements. It prefers fresh water grasslands below 2000 feet with plenty of California Voles running around. (About 1500 per hectare.)

Given the number of CBC counts in California that have White-tailed Kites there is a wide variety of kite density that can be found in California.

Activities

Pick different counts that have a wide variety of kite density: 1, 10, 30, 50 80, 100 kites per count. Anticipate what the environment looks like given the requirement of the number of kites.

If there are over 150 kites on the CBC that is prime kite environment.

If there are less than 10 then we might expect a small remnant of grassland.

Resources

12. Microtine Bust

Bibliography
Appendices
Lesson Plans
Table of Contents

Lesson Plan Name

Microtine Bust

Subject Area

Science

Topic Area

Life Science

Grade Level

9 - 12

Objectives

To understand the differences in the behavior of a predator specialist compared to a predator generalist.

Standards

Materials

Instructional Procedure

Imagine that the California Vole population has bottomed out. In this scenario there are only two voles per hectare. Their population will rebound next year but right now the rodent predators have to improvise.

Activities

Write a short essay that discusses life without the voles.

1. Describe the strategies of the specialist White-tailed Kite and the generalist Red-tailed Hawk.

2. How does life as a generalist compare to life as a specialist? What happens to the White-tailed Kite if it leaves its preferred habitat?

3. What does it mean to be a nomadic hunter?


Bibliography

Lesson Plans

Table of Contents

Appendices

A. White-tailed Kite Numbers in Selected California Christmas Bird Counts

D. 1996 CBC with observations of Northern Harriers

G. Conversion Tables

B. Highcounts for White-tailed Kites for each year

E. Statistics for California 1939 and 2004

H. Energetic Requirements for Hawks and Owls that eat primarily Microtene Rodents

C. Total Numbers for White-tailed Kite for 1960 - 2004 broken down by state.

F. Start year for Selected California CBCs

 

Resources
From the USGS - Avian Conservation Glossary
Biogeography Glossary

Comments and suggestions are gratefully welcomed. jlrosso@aol.com
 


A. White-tailed Kite Numbers in Selected California Christmas Bird Counts

Bibliography

Appendices

Lesson Plans

Table of Contents

Benicia
Palo Alto
Santa Barbara
San Jose
Folsom
Sacramento National Wildlife Refuge
Los Banos
Ano Nuevo
Peace Valley
Orange County (Coastal)

White-tailed Kite Numbers for the Benicia Christmas Bird Counts

Appendices
Table of Contents
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
67
23
34
74
70
33
72
38
49
99
41
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
52
72
88
84
118
65
120
111
67
106
107
1995
1996
1997
1998
1999
2000
2001
2002
2002
2003
2004
159
78
118
137
32
168
121
154
87
185

White-tailed Kite Numbers for the Sacramento National Wildlife Refuge Christmas Bird Counts

Appendices
Table of Contents
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
2
2
5
9
8
15
18
11
28
9
38
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
13
76
51
26
43
150
77
71
81
66
140
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
170
144
94
63
253
174
81
92
81
200
202
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
165
199
93
173
128
169
204
173
134
118
144
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
64
165
91
63
No Count
73
127
141
114
69
188

White-tailed Kite Numbers for the Los Banos Christmas Bird Counts

Appendices
Table of Contents
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
3
4
20
26
5
40
68
55
27
45
39
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
55
132
32
198
293
88
34
46
No count
32
41
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
38
57
30
25
72
94
82
62
59
67
73
2002
2003
2004

52
67
40

White-tailed Kite Numbers for the Folsom Christmas Bird Counts

Appendices
Table of Contents
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
2
13
20
13
31
25
40
13
23
17
23
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
44
7
20
41
42
35
28
59
40
39
12
2001
2002
2003
2004

61
No Count
29
30

White-tailed Kite Numbers for the Santa Barbara Christmas Bird Counts

Appendices
Table of Contents
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
9
17
75
7
33
53
22
23
22
26
40
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
25
39
84
98
51
47
42
23
37
40
45
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
29
21
21
18
18
12
10
4
No Count
No Count
24
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004

36
31
43
29
29
45
27
22
31
25

White-tailed Kite Numbers for the Palo Alto Christmas Bird Counts

Appendices
Table of Contents
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
3
3
6
1
1
3
17
25
10
45
13
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
22
15
13
14
34
48
32
18
6
19
36
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
14
19
35
55
27
31
20
21
15
19
14
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
14
21
19
15
26
22
27
34
28
26
28
2004

44

White-tailed Kite Numbers for the San Jose Christmas Bird Counts

Appendices
Table of Contents
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
4
0
0
0
0
0
0
0
0
1
0
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
0
0
2
0
0
0
0
0
2
1
12
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
3
1
6
0
10
10
7
9
11
5
15
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
44
17
25
13
27
18
29
57
8
18
34
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
56
63
29
12
12
47
65
45
55
55
72
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
49
60
43
22
20
13
31
21
19
42
13
1997
1998
1999
2000
2001
2002
2003
2004

19
12
16
18
17
32
28
48

White-tailed Kite Numbers for the Ano Nuevo Christmas Bird Counts

Appendices
Table of Contents
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
4
5
5
6
16
6
28
8
5
27
5
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
13
20
30
10
7
15
No count
31
21
9
16
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
6
41
16
55
42
25
44
32
13
40
35

White-tailed Kite Numbers for the Peace Valley Christmas Bird Counts

Appendices
Table of Contents
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
34
63
70
87
30
32
27
64
46
44
20
1985
1986
1887
1988
1989
1990
1991
1992
1993
1994
1995
58
33
21
36
18
4
29
20
18
54
65
1996
1997
1998
1999
2000
2001
2002
2003
2004

25
23
37
11
67
24
28
13
27

White-tailed Kite Numbers for the Orange County (Coastal) Christmas Bird Counts

Appendices

Table of Contents
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
0
0
0
0
0
0
2
3
1
0
2
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
5
1
15
15
0
28
11
14
34
9
8
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
10
11
10
18
28
34
41
22
27
27
33
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
14
54
51
38
31
29
53
53
48
49
55
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
9
12
20
15
6
16
15
4
17
36
25
1996
1997
1998
1999
2000
2001
2002
2003
2004

24
56
18
76
13
10
11
11
18


B. Highcounts for White-tailed Kites for CBC's between 1960 and 2004.

Appendices

Lesson Plans

Table of Contents

All locations are in California unless otherwise indicated (1992, 1997).
1960

1969

1978
Centerville Beach/120
1987
Sacramento/169
1996
Rio Cosumnes/84
1961

1970

1979
Sacramento/92
1988

1997
Corpus Christi(Tx)

110

1962

1971
Sacramento/140
1980
Centerville Beach/115
1989
Sacrmento/

204

1998

1963

1972
Sacramento/173
1981
Centerville/

137

1990
Sacramento/173
1999

1964

1973
Sacramento/134
1982
Sacramento

202

1991
Stockton/145
2000

1965

1974

1983

Los Banos

198
1992
Lagunna Atascosa (Tx)/157
2001

1966

1975
Santa Barbara/84
1984

1993

2002

1967

1976
Sacramento/253
1985
Caswell/218
1994

2003

1968

1977
Sacramento/174
1986

1995

2004


C. Total Numbers for White-tailed Kite (Black shouldered Kite) for 1960 - 2004 by state

Appendices

Lesson Plans

Table of Contents

Year

US total
California
Texas
Wash
Florida
Arizona
Louisiana
Oregon

1960

118
118
0
0
0
0
0
0

1961

92
81
11
0
0
0
0
0

1962

162
154
8
0
0
0
0
0

1963

127
125
2
0
0
0
0
0

1964

237
225
12
0
0
0
0
0

1965

235
232
3
0
0
0
0
0

1966

351
336
15
0
0
0
0
0

1967

362
311
51
0
0
0
0
0

1968

347
326
21
0
0
0
0
0

1969

379
359
18
0
0
0
0
0

1970

454
439
15
0
0
0
0
0

1971

669
620
49
0
0
0
0
0

1972

689
637
50
0
0
0
0
0

1973

656
604
52
0
0
0
0
0

1974

738
669
68
0
0
0
0
1

1975

951
875
75
0
1
0
0
0

1976

1580
1437
141
0
0
0
0
2

1977

1386
1275
102
0
0
0
0
8

1978

1176
952
201
0
0
0
0
23

1979

1031
799
210
0
0
0
0
22

1980

1413
1187
196
0
0
0
0
30

1981

2031
1807
213
0
1
0
0
10

1982

1666
1425
200
0
1
1
0
39

1983

1818
1484
298
0
0
0
0
34

1984

2457
2230
182
0
0
1
0
37

1985

2119
1940
141
0
0
4
1
31

1986

1769
1339
381
0
1
6
1
38

1987

1848
1395
380
0
0
10
0
62

1988

1896
1313
531
0
2
2
4
38

1989

1685
1231
368
0
1
4
17
54

1990

1356
1120
201
0
0
1
3
27

1991

1499
1188
260
0
0
1
7
42

1992

1516
1068
380
0
4
4
7
53

1993

1789
1195
505
0
2
6
7
72

1994

1627
1196
346
0
5
15
6
59

1995

2231
1794
370
0
4
11
10
42

1996

1640
1318
234
0
4
4
10
70

1997

1784
1419
265
0
3
7
8
82

1998

1915
1502
314
0
0
2
9
88

1999

1797
1368
292
0
3
9
14
111

2000

2388
1966
305
6
1
6
19
85

2001

2343
1950
238
7
4
3
36
104

2002

2174
1666
385
10
2
10
18
83

2003

1783
1385
279
11
1
4
12
91

2004

2418
2046
241
11
2
2
9
105

US Total
California
Texas
Washington
Florida
Arizona
Louisiana
Oregon


D. 1996 California Christmas Bird Count with observations of at least one Northern Harrier

Appendices

Lesson Plans

Table of Contents

1996 California Christmas Bird Count with observations of at least one Northern Harrier
Auburn
1
Los Angeles
1
Pasadena
3
Anza Borrego
3
Long Beach
3
Peace Valley
121
Angwin
9
Lake Henshaw
4
Red Bluff
9
Ano Nuevo
39
Lost Lake
25
Redding
1
Arcata
11
Lancaster
27
Redlands
2
Bakersfield
11
Lone Pine
8
Rancho Santa Fe
7
Big Bear Lake
0
Lake Almanor
1
Santa Ana River Valley
14
Benicia
268
Los Banos
161
Santa Barbara
16
Bear Valley
5
La Purisima
34
San Diego
43
Big Sur
10
LaGrange
42
San Francisco
7
Bishop
15
Marin County
39
Santa Maria
45
Butterbredt Springs
0
Moss Landing
25
Salton Sea North
16
Calaveras
0
Milburn
11
Santa Catalina
0
Centerville Beach
49
Mount Hamilton
1
San Jose
42
Contra Costa County
26
Mineral
0
South Fork Valley
11
Clear Lake
9
Majave River Valley
3
San Jacinto Lake
59
Claremont
3
Mono Lake
5
Sacramento
102
Chico
10
Mendocino
19
Sonora
0
China Lake
7
Modoc
48
San Bernardino
3
Carrizo Plains
14
Monterey
3
Springville
11
Crystal Springs
21
Moro Bay
41
Santa Rosa
10
Caswell
38
Mount Shasta
20
Salton Sea South
52
Death Valley
0
Malibu
10
Stockton
138
Escondido
9
Morongo Valley
3
San Juan Capistrano
4
Etna
2
Oakland
11
San Fernando Valley
9
Folsom
38
Orange County
38
Sierra Valley
5
Falls River Mills
148
Orange County (Northeast)
17
Tehachapi
4
Grass Mountain
3
Oroville
30
Tule Lake
81
Grass Valley
0
Oceanside
25
Thousand Oaks
34
Hayward
66
Palo Alto
30
Truckee
0
Honey Lake
27
Panoche Valley
4
Ukiah
4
Hollister
18
Putah Creek
15
Ventura
19
Idyllwild
0
Pinnacles
9
Willow Creek
0
Joshua Tree
0
Parkfield
4
Western Sonoma County
38
Kern River Valley
14
Palos Verdes
0
Yosemite
0
Lewiston
1
Point Reyes
78
Yreka
11
Out of 108 counts 95 counts had Northern Harriers present.


E. Statistics of California

Appendices

Lesson Plans

Table of Contents
Tabulation of Some Types of Land Areas in California
1939 - Jean Lindsdale (Condor, Vol. 39)
2004

Land Area of State:

99,617,280 Acres

Land Area of State:

Cultivatable Land

23,000,000

Land in 150,360 Farms

30,437,995

Land Drained for Agriculture

2,233,714

Potentially irrigable land

18,000,000

Area under irrigation

4,746,632

Non-agricultural land

76,000,000

Original forested area

23,000,000

Present forested area

18,270,000

Present virgin timber

13,200,000

20 National forests

19,164,573

Grazing land in forests

11,389,000

Public domain

15,676,000

People in California

5,677,251
People in California:
33,871,648 (2000)

Urban (73.3%)

4,160,596

Rural

1,516,655

Farm

620,506

Number per square mile

36.5

217.16 (2000)

Per cent increase in 10 years

65.7
Percent increase in 60 years:
338%

Hunters' licenses (1935)

189,125

15,822,356(1999)


F. Start Year for Selected California Christmas Bird Counts

Appendices

Lesson Plans

Table of Contents

Start Year for Selected California Christmas Bird Counts
Count Name
Year of First Count
Count Name
Year of First Count
Count Name
Year of First Count

Ano Nuevo

1972

Los Banos

1969

Peace Valley

1974

Auburn

1980

Marin

1976

Pt. Reyes

1971

Benicia

1973

Moss Landing

1976

Santa Barbara

1962

Centerville Beach

1963

Moro Bay

1949

Santa Maria

1980

Contra Costa

1956

Orange County (coastal)

1941

San Jacinto Lake

1981

Folsom

1979

Orange County

1947

Sacramento

1940

Hayward

1968

Oceanside

1951

Stockton

1950

Hollister

1986

Palo Alto

1960

Thousand Oaks

1975


G. Conversion Tables

Appendices

Lesson Plans

Table of Contents

640 Acres to 1 Square mile

Hectare equals 2.471 acres

Area of a circle, A = pi (r2)

pi = 3.14 (approximately)

Diameter of a CBC is 15 miles.

The radius (r) of a circle is half the diameter.

hectare = 100 M x 100 M


H. Selected Hawks and Owls of California that eat over 50% Voles

Appendices

Lesson Plans

Table of Contents

Hawks and Owls of California that eat over 50% Voles
Estimated grams per day that each species needs.
Estimated % of diet made up by voles

White-tailed Kite

77 grams
99

Red-tailed Hawk

100 grams
96

Red-shouldered Hawk

100 grams
96

Rough-legged Hawk

100 grams
96

Ferruginous Hawk

100 grams
96

Northern Harrier (Marsh Hawk)

95 grams
50

American Kestral

50 grams
60

Barn Owl

60 grams
84

Short-earred Owl

60 grams
84

Long-earred Owl

60 grams
84


Bibliography

Appendices

Table of Contents

Lesson Plans

American Ornithologists Union. 1983. Checklist of North American Birds - Sixth Edition. American Ornithologists' Union, Washington, D.C..

Bent, A. C. Life Histories of North American Birds of Prey, V. 1. Dover Publications. 1961

Clark, S. W. and B. K. Wheeler. Peterson Field Guides - Hawks Houghton Mifflin Company1987

CPIF (California Partners in Flight). 2000. Version 1.0. The draft grassland bird conservation plan: a strategy for protecting and managing grassland habitats and associated birds in California (B. Allen, lead author). Point Reyes Bird Observatory, Stinson Beach, Ca. http://www.prbo.org/CPIF/Consplan.html.

Dawson, W. L. The Birds of California, Volume 3. South Moulton Company, 1923.

del Hoyo, J., A. Elliot & J. Sargatal (Eds.) Handbook of the Birds of the World, Volume 2. Lynx Edicions. Barcelona 1994

Dunk, J. R. 1995. White-tailed Kite (Elanus leucurus). In The Birds of North America, No. 178 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.

Dunk, J. R., & R. J. Cooper. Territory-size Regulation in Black-shouldered Kites. Auk, Vol. 111. No. 3 July 1994

Ehrlich, P. R., D. S. Dobkin, & D. Wheye. The Birder's Handbook. New York. Fireside Book. 1988.

Ellis, D. H. & G. Monson. White-tailed Kite Records for Arizona. Western Birds, Vol. 10, No. 3, 1979.

Garbrielson, I. N. & S. G. Jewett. Birds of the Pacific Northwest. Dover Publications, New York. 1970

Gill, R. Jr. Breeding Avifauna of the South San Francisco Bay Estuary. Western Birds, Vol. 8, No. 1, 1977

Gilliard, T. E. Living Birds of the World. Garden City. Doubleday and Company. 1958

Greenberg, R. & S. Droege. On the Decline of the Rusty Blackbird and the Use of Ornithological Literature to Document Long-term Population Trends. Conservation Biology, Vol. 13, No. 3, June 1999; pgs. 553 - 559.

Grinnell, J. A Distributional List of the Birds of California. Cooper Ornithological Club. 1915

Grinnell, J & A. H. Miller. The Distribution of the Birds of California. Cooper Ornithological Club. 1944

Hamerstrom, F. Harrier - Hawk of the Marshes. Washington, D.C.. Smithsonian Institution Press. 1986.

Henny, C. J. & J. T. Annear. A White-tailed Kite Breeding Record for Oregon. Western Birds, Vol. 9, No.3, 1978 p. 131-132.

Hobbs, R. J. & H. A. Mooney. Broadening the Extinction Debate: Population Deletions and Additions in California and Western Australia. Conservation Biology, Vol. 12, No. 2, April 1998.

Hoffmann, R. Birds of the Pacific States. Houghton Mifflin Company. 1927.

Koenig, W. D. Spatial Autocorrelation in California Land Birds. Conservation Biology, Vol. 12, No. 3, June 1998; pgs. 612 - 619.

Koford, R. R., J. B. Dunning Jr., C. A. Ribic, & D. M. Finch. A Glossary for Avian Conservation Biology. Wilson Bulletin, 106 (1), 1994. pp. 121 - 137.

Appendices

Lesson Plans

Table of Contents

Top

Le Boeuf, B., and S. Kaza. The Natural History of Ano Nuevo. Pacific Grove. Boxwood Press, 1981

Linsdale, J. M. Preservation of Birds in California. Condor Vol. 39

MacArthur, R. H. Geographical Ecology - Patterns in the Distribution of Species. Princeton. Princeton University Press. 1972.

MacWhirter, R. B., and K. L. Bildstein. 1996. Northern Harrier (Circus cyaneus). In The Birds of North America, No. 210 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.

Moore, J. White-tailed Kite. http://www.prbo.org/calpif/htmldocs/species/grassland/wtkiacct.html Downloaded on 2/17/2005

Mowet, F. Never Cry Wolf

Newton, I. Population Ecology of Raptors Vermillion, North Dakota. Buteo Books, 1979.

Newton, I. Population Limitation in Birds. San Diego. Academic Press, 1998

Odum, E. P. Fundamentals of Ecology (Second Edition). Philadelphia. W. B. Saunders Company, 1959

Peronne, L. 2002. "Microtus californicus" (On-line), Animal Diversity Web. Accessed December 07, 2007 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Microtus_californicus.html

Peterson, R. T. A Field Guide to Western Birds. Houghton Mifflin Company, 1960

Pickwell, G. Requiem for the White-tailed Kites of Santa Clara County. Condor. 1931

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Shuford, W. D. The Marin County Breeding Bird Atlas. Bushtit Books. 1993.

Small, A. The Birds of California. Winchester Press, New York. 1974.

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Warner, J. S. & R. L. Rudd. Hunting by the White-tailed Kite (Elanus Leucurus). The Condor 1975

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