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A project of birdcentral.net
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Dr. Jim
Rosso
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jlrosso@aol.com
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Learning Science
through the Study of Birds
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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.
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Table of
Contents
Preface
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
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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
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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.
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 :
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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.
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From, Birds
of Prey of the World p. 207
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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.
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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:
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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.
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From, Birds
of Prey of the World , p. 209
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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.
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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
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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.
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From The
Birder's Handbook; p.
222
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Diet: Especially
California vole and other rodents, also birds, snakes,
lizards, frogs, and large insects.
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Hunting
From, Birds
of Prey of the World p. 209
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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.
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From Atlas
of the Breeding Birds of Monterey County,
California (1993) p. 88
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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.
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From Shuford, David W. (1993). Marin
County Breeding Bird Atlas. p. 133-135
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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.
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Habitat:
From California
Birds - Their Status and Distribution
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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.
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From The
Birder's Handbook p. 222
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Breeding Habitat: Savanna,
riparian woodland, marsh, partially cleared or cultivated
fields, grassy foothills.
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From Grinnell - (1944) The
Distribution of the Birds of California.
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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.
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Distribution:
From California
Birds - Their Status and Distribution
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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.
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From, Birds
of Prey of the World p. 209
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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.
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Small, Arnold California
Birds - Their Status and Distribution
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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.
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From The
Birder's Handbook p. 222
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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.
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From Atlas
of the Breeding Birds of Monterey County,
California (1993) p. 88
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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.
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Florence Merriam Bailey - (1902)
Handbook
of Birds of the Western United States
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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.
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Grinnell - (1915) A
Distributional List of the Birds of California
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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.
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Dawson - (1923) Birds
of California, Volume 3, p. 1649
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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."
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Hoffman - (1927) Birds
of the Pacific States p.
64
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There are probably not more
than fifty pairs left in California and in spite of
protection by law the number is slowly
decreasing.
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Grosvenor, National
Geographic Society's The Book of Birds
- 1939
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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.
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Grinnell - (1944) The
Distribution of the Birds of California.
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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.
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A. C. Bent , Life
Histories of North American Birds
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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.
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Ludlow Griscom Audubon's
Birds of America (1950)
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A rare and beautiful hawk
now almost extinct in the Southeast, a few in Texas and
California. Reapears in South America.
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From Atlas
of the Breeding Birds of Monterey County,
California (1993) p. 88
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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.
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From Shuford, David W. (1993). Marin
County Breeding Bird Atlas. p.
133-135
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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.
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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
|
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
|
|
|
|
|
|
|
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."
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
|
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.
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 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?
|
|
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
|
|
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
|
|
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
|
|
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
|
|
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.
|
|
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?
|
|
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
|
|
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
|
|
|
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
|
|
|
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
|
|
|
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?
|
Appendices
|
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
|
|
|
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
|
|
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
|
|
|
|
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
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
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
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
|
|
|
|
|
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
|
|
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
|
|
|
|
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
|
|
|
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
|
|
|
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
|
|
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.
|
|
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)
|
|
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
|
|
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
|
|
|
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
|
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