Adaptation - An organism's ability to exist in a particular environment comes from adjustments that they have made as a species. Owls have adapted to hunting at night by having large eyes (Barn Owl); many species use camouflage that helps them hide in their environment (American Bittern); a specially adapted beak that gives a species an advantage to feed on hard to reach organisms (Long-billed Curlew). All these special traits are considered adaptations. From A Dictionary of Birds: the production of fitness for a particular function, the term being also applied to a character (structure, behaviour, etc.) specially providing such fitness. 'Adaptive radiation' denotes divergence in the characters of related forms that enables them to exploit different kinds of opportunity. 'Convergence' denotes the adaptation of unrelated forms to similar functions, often giving rise to superficial resemblance."

From The Birdwatcher's Companion : "Adjustment, by an organism, sometimes in a striking and/or highly specialized way, to a particular way of life. A widely applicable term that may relate to structure, function, and/or behavior. Cryptic coloration, night vision, and canopy feeding, for example, are all adaptive characteristics of certain groups of birds.

Albinism - An abnormal lack of pigment. Albino Red-tailed Hawk

Allopatric - mutually exclusive geographically as contrasted with sympatric. From The Birdwatcher's Companion : Separated geographically; usually refers to closely related species or subspecies whose breeding ranges, although adjacent, do not overlap. In this situation the possibility of interbreeding cannot be tested because the two forms do not normally meet.

Alternate plumage - The spring plumage which is also referred to as the breeding plumage; the basic plumage is the plumage the bird has during the winter or the non-breeding time.

Altricial - Birds that are born without feathers, the ability to see, or the ability to feed themselves are called altricial. There are different levels of altricial young. Some are born with their eyes closed and no down, some have their eyes open and substantial down on them. But all altricial young need to be fed by their parents in contrast with precocial young which feed themselves within hours of being born. See Young birds.

American Ornithological Union - (From Wikipedia) The American Ornithologists' Union (AOU) is the oldest and largest ornithological organization in the Western Hemisphere. Unlike the National Audubon Society, its members are primarily professional ornithologists rather than amateur birdwatchers. It was founded in September 1883 by Elliott Coues, Joel Asaph Allen and William Brewster. Its quarterly journal, The Auk, has been published since January, 1884. Other significant publications include the AOU Checklist of North American Birds, which is the standard reference work for the field, and a monograph series, Ornithological Monographs.

Amphipods - From Wikipidia: "Marine amphipods may be pelagic (living in the water column) or benthic (living on the ocean bottom). Pelagic amphipods are eaten by seabirds, fish and marine mammals. Terrestrial amphipods such as sand fleas can often be seen amongst grains of sand and pebbles or on beaches.

Animals - Formerly the living world was divided into two kingdoms: animals and plants. All mammals are animals, but not all animals are mammals. Birds are animals. All birds are animals but not all animals are birds. All insects are animals but not all animals are insects. One of the most common mistakes made is to refer to "animals and birds" when they mean to say "mammals and birds."

Anting - An example of care behavior. From A New Dictionary of Birds: "This consists of special movements, apparently confined to passerines, whereby the defence and other body fluids of ants (Hymenoptera: Formicidae) are applied to the bird's feathers. The chief organic liquid involved is the formic acid produced by the worker (and queen) caste ants of species of the acid-ejecting Formicinae. ... The annointing of the feathers with ant fluids is effected either directly by the bird applying the ant to its plumage with its bill (active anting), or indirectly by its permitting the ants to swarm on it its plumage, ejecting formic acid (so-called passive anting)." Picture of American Robin anting.

Arthropods - Phylum of segmented animals that have hard outer skeletons. Phylum includes insects, arachnids, and crustaceans. There are over 1 million species in this phylum. This is the largest phylum of invertebrates.

Anthropomorphizing - Interpreting the behavior of non-human animals in terms of our understanding of human animals. There are some needs such as the need to eat, sleep, drink water, that are very similar between humans and non-human animals. In other cases the practice of interpreting animal behavior in human terms is not always warranted.

Audubon, John James - (1785 - 1851) Early American ornithologists and painter. He was one of the first to study the birds found in America. Some of his writing can be viewed in the natural history accounts of these species: Red-throated Loon, Great Egret, Snowy Egret, Black-crowned Night Heron, Roseate Spoonbill, White Ibis, Ring-necked Duck, Lesser Scaup, Mottled Duck, Mississippi Kite, Chipping Sparrow, Magnificent Frigatebird, Whooping Crane, Pileated Woodpecker, Florida Scrub Jay, Cliff Swallow, Western Tanager,

Audubon Society - Founded in 1896; the primary goal of the Audubon Society is to promote conservation of natural resources and encourage awareness of nature.

Avian Dispersal - Movement of individuals from an area of high intensity to areas of low intensity. Often this term refers to movement of recently fledged birds to an area other than where they were born.

Avian Intelligence - The intelligence of birds is difficult to define. To many scientists, when birds participate in problem solving, or demonstrate memory, or cognitive mapping, they demonstrate signs of intelligence. Some people argue that it is not intelligence, but rather advanced stimulus response. Some birds, such as members of the Corvidae family, demonstrate advanced memory and advanced problem solving. The natural history notes from Bent for the Common Grackle and Western Gull demonstrates what many would consider to be examples of avian intelligence. See Learning.

Aviary - A structure used to house birds. Many zoos have large aviaries that visitors may walk within and view the birds. The Rufous Hummingbird, Fulvous-Whistling Duck, Black-bellied Whistling Duck, Common Moorhen, Greater Flamingo, Yellow Grosbeak, Brewer's Sparrow, Hooded Oriole, were photographed in aviaries.

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Bailey, Florence Merriam - (1863 - 1948) American ornithologist, who wrote the Handbook of Birds of the Western United States in 1902. Sister of C. H. Merriam. First female member of the AOU. Some of her writing can be viewed in the natural history accounts of these species: Western Kingbird Scissor-tailed Flycatcher, White-tailed Ptarmigan, Scaled Quail, Bridled Titmouse, Cactus Wren, Curve-billed Thrasher, Phainapepla, Green-tailed Towhee,

Baird, Spencer - (1823 - 1887) Early American Ornithologist. The Baird's Sandpiper and Baird's Sparrow were named after him.

Banding - The science of studying birds by gathering data on their movements and age. This is done by putting a very light aluminum band around one of their legs. The band has a number which is recorded in a book with all appropriate data. When the bird dies or is recaptured the band is recovered and scientists retrieve data about how far the bird has traveled and how long it has lived, in addition to other data. This White-crowned Sparrow has a band on its leg. For a look at some of the work of a banding station check out this page from the Ft. Steven's banding station in the state of Washington.

Basic plumage - The plumage a bird has during its non-breeding time which is most of the year. The alternate plumage is the plumage during the breeding time.

Bathing - A type of care behavior for birds. From The Birdwatcher's Companion "Almost all birds wet their feathers in some manner on a regular basis as part of their ritual of plumage maintenance. Some desert birds seldom or never take water baths, and gallinaceous birds substitute dust baths at least in most instances. Most authorities seem to agree that birds bathe not as a direct cleaning process as humans do, but more as a preparation for preening and oiling the feathers. As is true of most other forms of bird behavior, bathing is not done haphazardly but rather in a sequence of characteristic gestures which vary consistently among different types of birds. Observations of both captive and wild young birds suggest that the urge to bathe is innate, though some of the particular gestures of the wetting and drying process may be learned or at least triggered by watching older individuals."

Beak - The jaws of the bird; the tool that the bird uses to eat with. The type of beak that the bird has determines the type of food that is easiest to eat. The Snail Kite has a beak that is especially adapted to eat large snails. The Long-billed Curlew has a beak that is specially adapted to probe deep in the sand, while the Black Turnstone has a beak that is good for turning over small stones. The Black Turnstone does not compete with the Curlew for food because it can't obtain the type of food that the Curlew eats. The Broad-billed Hummingbird cannot eat the seeds that the Black-headed Grosbeak eats. Different species that seem to have the same type of beak really are more different than we think and this helps them to not compete for the same type of food. (See Gause's Rule of Non-Competition)

Behavior - How an animal responds to the outside world. The behavior of a Black-necked Stilt is much different from the behavior of the Cooper's Hawk. Behavior is one of the themes included in the education section of birdcentral. Niko Tinbergen, Konrad Lorenz, and Karl Von Frisch received the 1973 Nobel Prize for the work they did determining how to conduct the study of behavior, ethology.

Bell, John - (1812 - 1889) American ornithologist and associate of John James Audubon. Bell's Vireo and Sage Sparrow (Amphispiza belli) were named after him. From The Birdwatcher's Companion "A well-known collector and taxidemist from New York State who accompanied his friend John James Audubon on the latter's expedition up the Missour River in 1843. He was also known and liked by eminent ornithologists of the next generation, e.g., Baird, Ridgway, Cassin, and Le Conte. Aududon named the vireo for him, Ridgeway the sparrow, and an ornithologist name Giraud added a Mexican warbler species now known as the Golden-browed Warbler (Basileuteris belli).

Bendire, Charles E. - (1836 - 1897) A Major in the US Army who started the Life Histories of North American Birds which became the 26-volume series finished by A. C. Bent. The Bendire's Thrasher was named after Bendire. Some of his writing can be viewed in the natural history accounts of these species: Yellow-billed Cuckoo, Lewis Woodpecker, Blue Jay, Eastern Wood Pewee, Vermillion Flycatcher, Florida Scrub Jay

Bent, Arthur C. - (1866 - 1954) Beginning in 1919 Arthur Cleveland Bent gathered information on the status of birds in the 48 states. This material, which when finished, consisted of 26 volumes, was published originally by the US Government and later republished by Dover Books as the Life Histories of North American Birds. A. C. Bent died in 1954 before the completion of the project which was finished in the 1960s by Oliver Austin Jr.. The Life Histories of North American Birds is one of the best sources of information on distribution, behavior, and food for each species. It also provides an historical context for understanding our views on natural resources and our efforts to maintain those resources.

Bergmann's Rule - (From The Birdwatcher's Companion ) "The observation (formulated by a nineteenth-century German Zoologist) that overall body size tends to be greater in representatives of bird and mammal species living permanently in cooler climates than in those living in warmer climates. Put simply, American Kestrels in Maine (Falco sparverius sparverius) are larger on the average than those in Florida (F. s paulus). The ecological principle followed is that large bodies retain heat more efficiently than small ones, and that there is therefore an adaptive size increase in populations constantly subjected to lower temperatures."

Biology - The study of living organisms. This includes, but is not restricted to, zoology and botany and other studies.

Biome - Plant communities such as chaparral, tundra, coniferous forest, deciduous forest, grassland, southwestern (U.S.) pine-oak woodland, pinyon-juniper woodland, chaparral, and desert. There are many different types of plant communities. They can be broken into eight large categories.

1. Grasslands which includes prairie grassland, tallgrass prairie, mixed grass prairie, short grass prairie
2. Forest which can be broken down into 18 types of forest: boreal forest, riparian woodland, western forest, northwestern coastal forest, open oak woodlands, pinyon juniper woodlands, eastern forest, northern hardwood forest mixed deciduous forest, coastal plain pine oak forest, savannah, subtropical forest, Florida subtropical hammock, mangrove swamps, and South Texas mesquite
3. Shrublands which includes chaparral and shrubland
4. The desert which includes Great Basin Desert, Mojave Desert, Sonoran Desert, Chihuahan desert
5. Tundra which can include Arctic tundra, low-arctic tundra, high arctic tundra, and alpine tundra
6. Wetlands and Aquatic habitat which includes rivers and streams, freshwater marsh, saltwater marsh, and lakes and ponds
7. Ocean habitat which includes coastal environment, and coastal waters and open ocean
8. Urban areas which includes farms, suburbia and cities.

One basic categorization of biomes lists five types:

• Aquatic,
• Deserts,
• Forests,
• Grasslands,
• Tundra.

Another way to categorize the biomes:

• Tundra and Arctic Deserts,
• Temperate Needleleaf Forests or Woodlands,
• Temperate Broadleaf Forests or Woodlands,
• Temperate Grasslands,
• Cold Winter Deserts and Semi-Deserts,
• Evergreen Forests
• Scrub or Woodland,
• Tropical Grasslands and Savanna,
• Warm Deserts and Semi-Deserts,
• Tropical Dry or Deciduous Forests or Woodlands,
• Tropical Humid Forests,
• Mixed Mountain and Highland Systems,
• Mixed Island Systems.

Another system includes 11 biomes. See also Life Zones which is a system developed by C. H. Merriam.

Bird lice - (From Encyclopedia Britannica) "any chewing louse (Mallophaga) living on birds. Probably all bird species have chewing lice. Bird lice feed on feathers, skin surface, and sometimes blood but normally are not harmful."

Bird-of-the-Year - An expression used to describe an individual bird that was born in the current year. The Heerman's Gull page shows a bird of the year.

Birdwatching - The art and science of observing birds. It is done by amateurs and professionals alike. In fact there are many people who are birdwatchers who don't even know that they are birdwatchers. Beyond Birding is a good source that looks at the possibilities of bird-watching.

Breeding - The process of raising a family of birds. It requires courtship, nesting, feeding, and dispersal. Many species migrate to their breeding grounds.

Brewer, Thomas - (1814 - 1880) - American ornithologist. The Brewer's Sparrow and Brewer's Blackbird were named after him.

Brood - The young hatched from a clutch of eggs; a species of bird may have two or even three broods in a single breeding season.

Brood-parasitism - When one species uses a different species to raise their young, quite often to the damage of the parenting species. This is generally seen in the US when the Brown-headed Cowbird lays its eggs in the nests of many species of songbirds, especially warblers. The warblers end up raising the cowbird instead of their own young. Young Brown Headed Cowbird being fed by Oregon Junco.

Brooks, Maj. Alan - (1869-1946) Canadian naturalist and artist. Some of his writing can be viewed in the natural history accounts of these species: Bufflehead,

Burroughs, John - (1837 - 1921) - A nineteenth century writer and naturalist who, along with John Muir, helped to convince President Theodore Roosevelt to protect Yosemite by making it a National Park. Burroughs wrote a series of 23 books which studied primarily plants and animals of the east. Some of his writing can be viewed in the natural history accounts of these species: Ruby-crowned Kinglet, Eastern Bluebird, Pygmy Owl.

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Camouflage - When the plumage of an animal resembles the habitat where it lives and makes it difficult for other animals to find it. Some birds are particularly good at camouflage such as the American Bittern.

Care behavior - How a bird maintains its body. Basic functions that most birds utilize to care for their feathers such as bathing, drying, head scratching, anting, preening, sunning, and dusting.

Drying	Sunning	Preening	Dusting	Bathing	Stretching

Carrion - Dead animals. With the exception of vultures, crows, jays, gulls and a few others, most birds will not eat dead animals.

Carnivorous - Animals whose diet consists primarily of other animals.

Cassin, John - (1813 - 1869) American ornithologist. Cassin's Finch, Cassin's Vireo, Cassin's Auklet, Cassin's Sparrow, and Cassin's Kingbird, are named after him. Curator of birds at the Philadelphia Academy of Natural Sciences. He named the Brewer's Sparrow, and the Rufous-crowned Sparrow.

Census - Determining the numbers of birds within a particular area (see Christmas Count).

Chaparral - A dry shrub land found in the west; manzanita, chamisal and mahogany are typical plants. Wrentit is a good typical bird of the chaparral.

Chapman, Frank - (1864 - 1945) Curator of birds for 54 years at the American Museum of Natural History. Author of Birds of Eastern North America along with other volumes. Responsible for initiating the Christmas Count. Some of his writing can be viewed in the natural history accounts of these species: White Pelican, White-faced Ibis, Carolina Wren, Yellow Warbler, Hooded Warbler,

Christmas Count - During the last two weeks of the year, since the beginning of the twentieth century, thousands of birdwatchers census the birds found within their neighborhoods. Each location throughout the United States picks a single day to count the birds in a circle with a fifteen mile diameter.

Class - In the phylum vertebrates, there are five classes: fish, amphibians, reptiles, birds, and mammals. (Kingdom, Phylum, Class, Order, Family, Genus, Species)

Classification - The process of organizing the species. In the animal world the classification system uses Kingdom, Phylum, Class, Order, Family, Genus, Species. In the study of birds, the Kingdom = Animal Kingdom, Phylum = Vertebrates (animals with backbones), Class = Birds. In the study of North American birds we are currently (2006) recognizing 19 Orders and 67 families of birds. Classification is one aspect of zoology that is changing as we learn more about DNA and we use DNA/DNA comparison to re-evaluate which species is related to which. Classification expresses how we imagine nature is structured. (Kingdom, Phylum, Class, Order, Family, Species)

Cline - From A New Dictionary of Birds: "Term introduced by J.S. Huxley (1939) for a population aggregate (within a species) showing gradation in its characters from one end of its range to the other. A cline has itself no status in nomenclature. It may include forms to which subspecific names have been attached, although where the gradation is continuous (as happens in the absence of barriers) the validty of such subspecies becomes questionable. Nevertheless, the forms at the extremities of a cline may show striking differences when directly compared with each other, and this may be true also of intermediate forms taken from points sufficiently far apart in the clinal range. in such cases the use of subspecific names may have a practical convenience in providing taxonomic points of reference."

Clutch Size - The number of eggs within a nest.

Color - The color we see when we view a bird. This can be more complicated than we imagine. The color of everything that we see is the result of the light waves that are reflected back to us. If we see a white bird such as the Gt. Egret , then all the light waves are being reflected back to us. When we see colors other than white there are two basic causes: structural colors and pigmental colors.

The color of a bird is the result of pigmentation and structural colors. Most of the colors that we see on a bird are the result of pigments. Structural colors, blue, black, and green, are either the result of interference (iridescence) or micro-structures of the feathers themselves. Iridescent colors are the result of lightwaves that interfere with each other. When we see the brilliant color of the Rufous Hummingbird that is the result of iridescence. Also when we see a Common Raven in the right light we see iridescence in its feathers.

As field ornithologists we have to realize that the color we see on a bird is quite often the result of the time of day that we see the bird. In the late afternoon colors can become a lot warmer. Take a look at the Marbled Godwit page and compare the pictures in the top right corner and the bottom left corner. It is the same species but it has been photographed at different times of the day producing different colors. The pictures on the bottom left were photographed in late afternoon and produce a warmer color.

Community - Refers to organisms living within a defined habitat. Organisms within a freshwater marsh are related in many ways, one of which is being part of a food web. Within many communities different bird species will feed together and benefit from the cooperation. Community ecology is a branch of science that studies the patterns of community members.

Comstock, Anna Botsford -  (1854 - 1930) - Comstock was a pioneer in the field of nature education. She is famous for being one of the first to bring her students and other teachers out-of-doors to study nature. She wrote Handbook of Nature Study , in 1911. First female professor at Cornell; In 1923, she was nominated by the National League of Women Voters as being among the twelve greatest women of the country.

Congeners - The species of birds that are all in the same genus. The Black-bellied Plover (Pluvialis squatarola) and Pacific Golden Plover (Pluvialis fulva) are congeners in the genus Pluvialis. But the other plovers, Semi-palmated (Charadrius semipalmatus), Snowy (Charadrius alexandrinus), Killdeer (Charadrius vociferus) and Mountain (Charadrius montanus) are congeners of a different genus, Charadrius.

Convergent Evolution - "The independent evolution of structural or functional similarity among unrelated groups." Introduction to California Birdlife, Jules Evens and Ian Tait.. For an example look at the Tri-colored Heron and the Green Heron. Two different species that have similar hunting techniques in the same habitat.

Coues, Elliot - (1842 - 1899) - American ornithologists. Coues Flycatcher (now named Greater Pewee, Contopus pertinax) was named after him. Author of a variety of books including Birds of the Northwest and New England Birdlife. Some of his writing can be viewed in the natural history accounts of these species: Snow Goose, Gambel's Quail, Pacific Loon, Tri-colored Blackbird,

Courtship - The behavior that various animals (usually males) utilize to attract a mate.

Crustaceans - Arthropods such as crabs, lobsters, shrimp; have a hard outer shell.

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DDT - dichlorodiphenyltrichloroethane - A pesticide that was responsible for eradicating malaria, but is also thought to be responsible for egg thinning amongst fish-eating birds such as the Osprey and the Bald Eagle. When parent birds sat on the eggs, the eggs broke because of the thin shell. It was banned during the 1970s.

Darwin, Charles - (1809 - 1882) - English naturalist who is considered to be most responsible for recognizing the forces of evolution.

Dawson, Leon - (1873 - 1929) - Ornithologist who specialized in studying the birds of the Northwest states and wrote Birds of Washington; also wrote a three volume work, Birds of California. Some of his writing can be viewed in the natural history accounts of these species: Vermillion Flycatcher, California Quail, California Condor, Brewer's Blackbird, Marsh Wren, Hermit Thrush, Townsend's Solitaire,

Decurved - Describes a beak that is curved down as in the Long-billed Curlew, Whimbrel, White Ibis etc.

Desert - One of the types of biomes, marked by limited water, and seasonal heat and cold. "The geographical, geological, and other natural history features of our desert domains are so varied and with them are bound up so many entrancing problems that fifty years of intimate acquaintance and wide travel over the arid Southwest have not desiccated my ardor for continued study and wide wanderings nor lessened my eagerness to lead others to the heart of my kingdom of joy. The question 'What is a desert?' cannot be answered without facing many difficulties. The term desert does not necessarily imply paucity of life, continuous heat, marked lack of moisture, or the presence of sandy wastes, although all these phenomena may occur. Even meagerness of rainfall is not always the deciding factor in the making of deserts but is only one of a combination of factors. Rocky or alkaline soils and continuous winds are features which play no minor role. For our present purposes, deserts may be defined as places of high, diurnal, summer temperatures, with more or less steady, drying winds and slight rainfall (generally under ten inches a year) and that unevenly and, from the standpoint of all but specialized plants and animals, often very unsatisfactorily distributed." Edmund C. Jaeger, The California Deserts.

Desertification -  A term used to indicate a habitat that has been degraded. It seems to be used by people who do not appreciate the true quality of a desert. A desert, as seen in California, Nevada, New Mexico etc. is a natural habitat that is inhabited by many species that have spent thousands of years developing adaptations to a web of other creatures who have adapted to the desert. The Yucca Moth and the Yucca have a very specialized relationship. Anybody who has visited the deserts, read Edmund Jaeger, spent anytime studying the inhabitants of a true desert, realize the biotic wealth of the area. The Cactus Wren, Road runner, Rock Wren, Scott's Oriole, Poorwill, Costa's Hummingbird, Ladder-backed Woodpecker, Black-tailed Gnatcatcher, and so many other animals and plants do not inhabit a wasteland. They inhabit the desert. The migratory birds that stop in at the desert oasis for a drink of water appreciate the opportunity as they fly from South America to breed in our northern forests. If we wish to indicate a habitat that has been destroyed through human activities then we should just call it a wasteland; a habitat that has been wasted.

Diptera - Large order of insects; true flies including house flies, and blood sucking flies such as mosquitoes and midges, etc.

Disease - (From A New Dictionary of Birds (1964) edited by Sir A. Landsborough Thomson and published by the British Ornithologists Union; The Disease essay is written by Arthur Ramsden Jennings). (This is portions of the Disease essay written by Arthur Ramsden Jennings) "ill health in any of the many forms from which birds, like all other animals may at times suffer. The casuses of disease may be divided into immediate (or exciting) causes and predisposing causes. The chief predisposing factors in bird diseases are bad environmental conditions and adverse changes in food supply.

Climatic changes and food supply are often linked. The bird's resistance to disease may be lowered by poor nutrition or by sudden changes in the temperature; thus abnormal heat or abnormal cold may cause heavy losses either directly or by predisposing to infectious disease. Sustained wet and cold weather is liable to bring on diseases of the lungs, which are a common source of trouble in chicks, especially amongst the nidifugous species.

Some of the more commonly encountered diseases of wild birds, other than those due to metazoan parasites, are described below. These conditions also occur in domestic and caged birds, but the emphasis here has been placed on the free-living wild bird.

• Aspergillosis - This disease is due to infection with a mould, usually Asperfillus fumigatus, which is commonly present in decaying vegetable matter.
• Botulism - An anaerobic bacterial organism, Clostridium botulinum Type C, produces a very powerful exotoxin that is responsible for a serious type of food-poisoning in many species of animals, including birds and man.
• Candida albicans Infection - This fungus sometimes causes disease of the mouth and crop of birds, a condition called 'thrush' or 'canker' by the bird-keeper. In young birds it sometimes cases serious losses.
• Deficiency diseases - Lack or imbalance of amino-acids, proteins, carbohydrates, fats, minerals, water, and vitamins may lead to disease.
• Encephalitis - Inflammation of the brain occurs in birds, and one specific form of this is due to a virus.
• Erysipelas Infection - The micro-organism Erysipelothrix rhusiopathiae usually produces a fatal septicaemia. Most species of mammals, birds and fishes seem to be susceptible to infection with this organism which can live for long periods in the soil and probably gets into the body through small abrasions and wounds.
• Fowl Leucosis - The term 'leucosis complex' refers to a group of diseases characterized by an abnormal production of the white blood cells and consequent changes in the organs and tissues.
• Fowl-plague - This is a most serious virus infection of domestic fowls, but most other birds are fairly resistant. The disease spread rapidly in fowls and produces a high mortality.
• Fowl-pox - This is a virus infection of the skin, especially of the head and feet, of birds. it is a common disease and has been recorded in many species.
• Lead Poisoning - This is common in waterfowl in America and is a serious source of loss. (Since the publication of this book, lead shot has been outlawed.)
• Newcastle Disease - Caused by a virus, this is one of the most serious diseases of domestic poultry and has a world-wide distribution.
• Pasteurellosis - Pasteurella pseudotuberculosis is a common pathogen of wildlife.
• Protozoal Infections - Many protozoa parasitise birds, but few of them are pathogenic. They are to be found in many tissues of the body.
• Psittacosis - This is a disease caused by a very large virus, and epidemics of psittacosis have been described in captive and free-living wild birds.
• Quail Disease - Enzootics of a highly fatal disease in the American Bobwhite Colinus virginianus and some species of grouse (Tetraonidae) have been described.
• Salmonellosis - Infections of birds with Salmonella organisms are common and important problems in the poultry industry.
• Tuberculosis - The avian type of Mycobaterium tuberculosis is a common cause of tuberculosis in birds, which become infected by ingestion.
• Tumours - Neoplasms (malignant new growths) are common in birds, and many different forms occur.
• Vesicular Dermatitis - This term is applied to a skin disease that is due to one or more viruses and occurs in several species of wild birds, including the Manx Shearwater (Puffinus puffinus) and other water birds.

 Distribution - How various species are scattered about the globe. Some species have a very narrow distribution. In the United States the Limpkin is only found in Florida. Other species such as the Great Blue Heron are found in all 50 states. Species such as the House Finch over the past 40 years has been gradually increasing their distribution from the western US to include the eastern US.

From A Dictionary of Birds: "The distribution of species or other categories considered in broad terms of range. Since local abudance and local distribution within the limits of the range depend on ecological factors, the range may be limited by the same factors, such as climate or its effect on habitats, habitat availability, or presence of competitors, predators, or prey. Ecology and Zoogeography thus have broadly overlapping interests. The range boundaries may, however, also be set by evolutionary history, plate tectonics, effective dispersal barriers, or the different dispersal abilities of species.

"Zoogeographical studies address themsevles to various aspects of gographical distribution. the time scale examined may vary from a static 'snap-shot' view of the present distribution to millions of years, and the geographical focus of interest may range from global distribution to distribution on islands or to dynamics of a portion of the range boudnary. In addition, the emphasis may be qualitative or quantitative.

"In terms of scientific research and the philosopohy of science, a distinction can be made betwen descriptive, analytic, and predictive zoogeogrphy. The descriptive view recrods facts of distribution , past or present. Analytic zoogeogrphy attempts to relate results of descriptive studies to various causes, ecological or historical. Predictive zoogeography uses theoretical, often mathematically formulated, models in order to derive predictions on patterns of goegrpahical distritution. In recent years, analytic and predcitive aspects of zoogeogrphy have developed rapidly, and, at the same time, quantitative approaches and population biology have been increasingly used in order to understand distribution patterns.

DNA - The chemical code that determines an individual's uniqueness. All vertebrates are the result of a combination of their parent's DNA. (See classification)

Drinking - From the Cambridge Encyclopedia of Ornithology "Drinking is necessary only if the food does not provide enough water to balance any loss that occurs by excretion or evaporation through the lungs - birds do not sweat and do not normally produce liquid urine. The frequency of drinking depends on the type of food and the bird's ecology; most seed-eaters need to drink at least once a day and may take in about 10% of their body weight, but some small birds of arid regions, such as the Zebra Finch and Budgerigar, can survive for many months on dry seeds without drinking or losing body weight. Presumably they can adequately supplement low dietary moisture with water produced internally through metabolism.

"The method of drinking varies. 'Sipping and tilting' is the commonest - the bill is dipped in the water, a sip taken and the head raised so that water trickles down the throat by gravity.

"Marine species have particular problems with drinking in that they take in salt with their food or drinking water. Small species are more sensitive to salt stress than larger ones and most marine ducks, for instance, are quite big. The salt is eliminated by the excretion of a concentrated solution through glands that have been inherited from the birds' reptilian ancestors and are situated just beneath the skin above the eyes. A duct from each gland leads into the nose from which saline fluid flows down the bill and is removed when the bird shakes its head."

Dusting - A type of care behavior in which certain species of birds roll their bodies in dirt to help in their battles with external parasites. Examples of this can be seen in the House Sparrow and the California Quail.

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Eclipse plumage - A post breeding plumage that occurs in some species; often refers to plumage that male ducks have between their breeding plumage and their non-breeding plumage; some species of ducks are unable to fly during this plumage.

Ecology - Study of the interrelationships between plants and animals with their physical environment. When we read in the A.C. Bent text for the Indigo Bunting how the bunting's population increases in areas of secondary growth, we are studying the species from an ecological perspective (Bent uses an excellent article written by James Bond). The word, ecology, has been misunderstood by many people. Ecology is neither good nor bad. It is a science used to study the relationship between organisms and their physical environment. From A New Dictionary of Birds - portions of the Ecology essay written by Robert MacArthur: the study of plants and animals in relation to their environment... As regards birds, it is well known that each species breeds and spends the winter, respectively, in characteristic areas of the earth; these areas, which in some instances are the same, form the geographical distribution of the species. Within the areas, the species will occupy only certain habitats; and within the habitats, each species has a characteristic behavior and abundance. The explanation of these patterns of distribution and abundance is the main problem of avian ecology.

Ecological niche -

Ecosystem - The totality of factors of all kinds that make up a particular environment.

Ecotone - The edge of a habitat; quite often the edge between two different habitats.

Endangered - When a population of a species is at a point that the species may not exist for too many more years, it is determined to be an endangered species. Examples of endangered species would be: California Condor, Clapper Rail. Some members of the Endangered List have been removed such as the Bald Eagle, and the Brown Pelican.

Endemic - Found only in certain areas. The Yellow-billed Magpie is only found in the state of California, so it is endemic to California. The American Magpie is found in many states so it is not endemic.

Ethology - The study of animal behavior under natural conditions. Niko Tinbergen, Konrad Lorenz and Karl Von Frisch are considered the originators of this science, and they received the Nobel Prize in Medicine in 1973 for their work.

Evolution - The process that leads to speciation. Evolution is the central theme of the study of biology. From A New Dictionary of Birds: "The theory which states that the different kinds of living tings have been produced by descent with modification from previously existing forms, not by each one being created separately with its present characters."

Evolution of birdlife - (From The Birdwatcher's Companion )

Major Trends/Events	Evolution of Birdlife
Paleozoic Era: 600 million to 225 million yhears ago
Evolution of life from earliest marine plants and invertebrates to presence of all current invertebrate classes plus fishes, amphibians, and reptiles. Reptiles emerged in the Pennsylvanian (late Carboniferous) Period (about 300 million years ago) and by the end of the Permian Period (280 to 225 million years ago) had greatly diversified.

Mesozoic Era: 225 million to 195 million years ago
Triassic Period: 225 million to 195 million years ago
North American climate mild; deserts extensive. forests of conifers and cyads; tree ferns and horsetails abundant. Amphibians decline; dinosaurs (including tecodonts) dominant by end of period.	No birds
Jurassic Period: 195 million to 135 million years ago
Sierra Nevada and Cascades araise. Climate mild; deserts widespread. Cycads dominatn plants; confiers still abundant. Age of Reptiles: present on land, in sea, and in air; great dinosaurs.	Archeopteryx: first known bird.
Cretaceous Period: 135 million to 70 million years ago
50 percent of North America under water; extensive limestone deposists/fossil beds laid down in West. Rockies arise. Climate turns cold late in period. Flowering plants appear; deciduous forests become dominant; sequoias widespread. Tyrannosaurus and other dinosaurs thrive at first, becoming extinct by end of period. Marsupials and primitive placental mammals evolve.	Apatornis, Baptornis, Hesperonis, and Ichthyornis. Also birds resembling modern loons, cormorants, ibises, rails, and sandpipers.
Cenozoic Era: 70 million years ago to present.
Tertiary Period
Paleocene/Eocene Epoch 70 million to 38 million years ago
Early mountain building followed by erosion; much of Atlantic and Gulf lowlands submerged. Seed-bearing plants continue dominant. Early 1-foot high horse (Eohippus), camels, elephants, dogs, cats evolve.	Few bird fossils from Paleocene: first hawks, also loons, tropicbirds, vultures, gulls, and terns. Eocene sees major evolution of birdlife, with nearly all known orders established by its close: albatrosses, pelicans, ibises, flamingos, grouse, pheasants, cranes, auks, cuckoos, owls, kingfishers, and a few passerines (e.g., starlings); also Diatryma, Neocathartes.
Oligocene Epoch: 38 million to 26 million years ago
Coastal lowlands emerge; active vulcanism along Pacific coast. Climate continues mild. Modern-type forests. Mammals dominant, especially cat and dog families; also three-toes horse, mastodon, antrhopoid ape.	First known grebes, shearwaters, boobies, storks, turkeys, limpkins, plovers, parrots, pigeons, nightjars, swifts, Old World warblers, and ploceid sparrows. A few genera of present-day birds appear. Many species of cranes and rails.
Miocene Epoch: 26 million to 12 million years ago
Sierras and Rockies rise again. North America at first very warm, cooling toward end. Forests reduced, plains and deserts arise. More modern tree species evolve. Golden Age of Mammals: great diversity of camels, great ape in Europe.	Most modern bird families probably exist; more modern genera evolve.
Pliocene Epoch: 12 million to 2-3 million years ago
Last lifting of Appalachians, Rockies, Sierras, Cascades. Climate continues to cool. Mastodons migrate from Old World to New; forerunner of modern horse; gorilla; beginning of Old Stone Age.	Birds reach maximum diversity; emergence of many modern genera and species. Moas, ostriches, rheas, tinamous, larks, swallow, nuthatches, emberizids, and (perhaps) woodpeckers appear.
Quarternary Period
Pleistocene Epoch: 2-3 million years ago to 10 thousand years ago
Ice Age: glaciers cover northern half of North America 4-5 times, greatly altering earth's surface;Great Lakes, many other modern gological features formed. Climate cold except for tropics. Four species of elephants, camels, saber-toothed tider in North America early in epoch; many large mammals and otehr forms dies out with advance of ice. Rise of Homo.	All modern birds in existence by end of epoch. Glaciation causes: demise of some large, ancient forms; division of populations in North America, promotoing speciation; retreat of species from North, perhaps leading to evolution of migration.

Extirpated - Extinct from a particular region. The Sharp-tailed Grouse has been extirpated from California.

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Family - The classification level between Order and Genus. Depending on which system you follow there are approximately 143 families of birds in the world and 67 families of birds in the United States. In the US Recurvirostidae is the family that includes the two species, American Avocet and the Black-necked Stilt. From A New Dictionary of Birds: "A primary taxonomic category (or a particular example therof), being a subdivision of an order and a grouping of genera." (Kingdom, Phylum, Class, Order, Family, Genus, Species)

Feather - There are three main types of feathers on a bird's body: down, contour, and flight. From A New Dictionary of Birds: "The component unit of the plumage and a structure outstandingly and uniquely characteristic of birds as a class. "

From Wikipedia: Feathers are among the most complex structural organs found in vertebrates: integumentary appendages, formed by controlled proliferation of cells in the epidermis, or outer skin layer, that produce keratin proteins. The ß-keratins in feathers, beaks and claws — and the claws, scales and shells of reptiles — are composed of protein strands hydrogen-bonded into ß-pleated sheets, which are then further twisted and crosslinked by disulfide bridges into structures even tougher than the a-keratins of mammalian hair, horns and hoof.

Feathers insulate birds from water and cold temperatures. Individual feathers in the wings and tail play important roles in controlling flight. These have their own identity and are not just randomly distributed. Some species have a crest of feathers on their heads. Although feathers are light, a bird's plumage weighs two or three times more than its skeleton, since many bones are hollow and contain air sacs. Color patterns serve as camouflage against predators for birds in their habitats, and by predators looking for a meal. As with fish, the top and bottom colors may be different to provide camouflage during flight. Striking differences in feather patterns and colors are part of the sexual dimorphism of many bird species and are particularly important in selection of mating pairs. The remarkable colors and feather sizes of some species have never been fully explained.

Feather tracts - The bird's body is not covered with feathers, but instead has tracts from which the feathers come from and cover the entire body. In between the tracts is bare skin.

Feeding - The process of acquiring food. Some animals specialize in particular types of food. Animals that specialize in fish are called piscivorous; animals that specialize in insects are called insectivorous. Omnivorous describes the many species of animals that feed on what is available. The American Crow is omnivorous.

• Insectivorous - Refers to animals that primarily eat insects. Flycatchers and swallows are good examples of insectivorous birds.
• Piscivorous - Animals that eat primarily fish, such as the Osprey.
• Nectivorous - Animals, such as the hummingbird, that feed primarily on nectar that they get from flowers.
• Granivorous - Animals that eat primarily seeds such as sparrows and finches.
• Frugivorous - Animals that feed largely on fruit. Birds that are frugivorous include orioles, tanagers (Summer Tanager) jays (Green Jay) etc.
• Herbivorous - Animals that eat plants such as grouse and ptarmigan
• Omnivorous - Refers to animals that eat everything. They eat plant food, fish, mammals, birds, etc. and will scavenge food. Gulls (Western Gull, etc.) are good examples of omnivorous feeders; also the Great-tailed Grackle. Most species are more specific about what they eat.  

From The Birdwatcher's Companion "Some of the methods and 'tools' by which birds search out and obtain their food are more complex and/or less obvious to the casual observer and merit a brief discription.

"Flight Mannerisms - An unusually slow flight has evolved in the harriers and the Turkey Vulture as a means of effectively scnning larage areas for their preferred prey. Some seabirds, most buteos and vultures soar on riaing air currents for a similar purpose. And the American Kestral, some hawks and kingfishers hover in midair, keeping their heads stationary to watch for movements of small, quick prey below.

"Nightjars - have small bills but enormous gapes (2 inches fully opened in Chuck-will's-widow) and fly through the air with their mouths open, swallowing numbers of insects (from tiny flies to large beetles) and even an occasional small bird. It has been widely suggested- but not conclusively shown - that the long, stiff, modified feathers (rictal bristles) that border the upper half of the gape in most nightjar species serve to enlarge their effective 'funnel' and also detect the presence of insects flying nearby in the dark. The latter hypothesis gains some support in the fact that the nighthawks (genus Chordeiles), which on the average fly during daylight hours more frequently than other nightjars, lack rictal bristles.

"Canopy Feeding - is practiced by some heron species and consists of raising the wings to create a shadow over shallow water. This may serve the dual purpose of attracting fish and cutting surface glare for the heron.

"Foot movements - are used in several bird families to flush prey within reach. Herons and some shorebirds stir the bottom in shallow pools and pick up any disturbed invertebrates. The characteristic 'spinning' of phalaropes is an elaboration of this technique. Some gulls are reputed to 'paddle' the earth with their feet to bring earthworms to the surface. And 'foot flushing' is also recorded in some ground-feeding songbirds.

"The Long Tongues - of most woodpeckers and hummingbird species can be extended into a tree cavity or flower calyx as much as several inches with the aid of an extendible bone and muscle structure known as the hyoid apparatus. This mechanism is attached at the base of the tongue, coils around the back and top of the skull, and is achored at the nostrils. The actual tongues of these birds bear a variety of specializations - barbs, brushes, grooves, saliva - that help capture and/or swallow particular food types.

"Wing Flashing - i.e., lifting the wings suddenly, is apparantly used by species of herons and mockingbirds to startle aquatic life and insects into motion, so that they can be seen and eatern. Mockingbirds also use this gesture in confrontations with snakes and other threatening situations.

"The Bills of Avocets - are strongly recurved toward the tip and vertically flattened. when a bird lowers its bill into the water, the upturned third of the bill becomes parallel to the surface and is swept rapidly back and forth admidst the surface algae or in bottom sediment and vegetation. When live organisms (small fish, mollusks, crustaceans, etc.) are felt by the bill, the mandibles close on the prey.

"The Bills of Spoonbills - are strongly flattened vertically and widened into a spatula shape at the tip. The interior of the 'spoon' is lined with sensitized tissue. Spoonbills feed by wading in shallow water and sweeping their partially opened bills from side to side in bottom sediment and vegetation. When live organisms (small fish, mollusks, curstaceans, etc.) are felt by the bill, the mandibles close on the prey.

"Skimmers - are unique in having a lower mandible which is significantly longer than the upper - an adaptation to an equally unique method of feeding. The birds fly low over calm water (often at dawn, and dusk and in flocks) and 'shear' the surface with the tip of the lower mandible, which is laterally flattened to nearly razor sharpness. When a fish or other edible object is encountered by this blade, the upper mandible closes down on it instantly. Skimmers will often retrace a stretch of water they have just 'plowed', apparently to take advantage of fish which rise to investigate the initial disturbance."

Fledge - (fledged, fledgling) - When a bird has left the nest it has fledged (White-crowned Sparrow). While it is in the nest it is a nestling. As a fledgling it is out in the world though it may still be fed by its parents (Elegant Tern) (Bullock's Oriole). This is probably the most dangerous period of time for a young bird. The relationship between the adult bird and the young varies with each different species during this time.

Foraging - The different behavior used by birds to find food. Basically there are two main categories of foraging: feeding from the air and feeding from a surface. Feeding from a surface can be classified as gleaning (Yellow-rumped Warbler), reaching (Little Blue Heron), hang gleaning, lunging. Feeding from a surface to under the surface can be classified as probing (Brown Creeper), gaping, pecking (woodpeckers), chiseling, hammering (woodpeckers, chickadees, titmouse), flaking (woodpecker), prying (woodpecker) and scratching. Aerial maneuvers can be defined as sallying, flutter chase, flush, pursue, hover gleaning (Blue-gray Gnatcatcher), and screen.

Forbush, Edward Howe - (1858 - 1929) - Author of Useful Birds and Their Protection, published by the Massachusetts State Board of Agriculture (1907). Some of his writing can be viewed in the natural history accounts of these species: Trumpeter Swan, Chipping Sparrow, Black-bellied Plover, Winter Wren, Golden-crowned Kinglet, Starling, Yellow-rumped Warbler, Black-throated Green Warbler, Chestnut-sided Warbler, Northern Waterthrush, Scarlet Tanager, Purple Martin,

From Wikipedia: Edward Howe Forbush (April 28, 1858 – March 7, 1929) was a noted Massachusetts ornithologist and a prolific writer, best known for his book Birds of New England. Born in Quincy, Massachusetts, in 1858, he was a precocious naturalist. His family moved to West Roxbury, when he was seven. As an older child, he conducted field studies of area wildlife and also studied taxidermy. Once again, his family moved to Worcester, where he became a member of the Worcester Natural History Society, and began to publish the results of his studies. At the age of sixteen he was appointed Curator of Ornithology of the Society's museum. When he was nineteen, he mounted an expedition to Florida — this would be the first of many trips he took around the United States to study birds. In 1893, Forbush was appointed Ornithologist to the Massachusetts State Board of Agriculture. His primary studies at this time were "economic ornithology" — that is, determining whether a given species of bird was beneficial or detrimental to agriculture. In 1908 he became the Massachusetts State Ornithologist. He was a founder of the Massachusetts Audubon Society. He was also first president of the Northeastern Bird-Banding Association (now the Association of Field Ornithologists). His work "Birds of Massachusetts (and Other New England States)" is a three-volume set of books published 1925–1929 by the Massachusetts Department of Agriculture. Title notwithstanding, it was and remains a valuable reference regarding not just New England birds but also in regard to ornithology of the Northeast and farther afield. He died in Westboro in 1929. In 1931, The Forbush Bird Club of Worcester, Mass., was established in his memory.

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 Gause's Rule of Non-Competition - From A Dictionary of Birds (Campbell and Lack, Eds): "In 1934 G.F. Gause wrote: 'As a result of competition two similar species scarecely ever occupy similar niches, but displace each other in such a manner that each takes possession of certain peculiar kinds of foods and modes of life in which it has an advantage over its competitor'. Gause's rule is often paraphrased as: 'Species with similar (or the same) ecological niches cannot coexist'; and as its corollary 'Coexisting species differ in their ecology.' Gause's rule is useful as a general statement: but it is not a testable hypothesis in normal scientific terms, because its reasoning is circular. if species coexist, they must be sufficiently different: if they do not coexist, they are too similar. Unless the terms 'similar' and 'different' can be made more precise, there is no way out of this impass."

Genus - The level of classification between Family and Species. Within the family Anatidae (the Ducks, Geese, Swans) there is the genus Anus which includes the Mallard, Shoveler, and teals and other ducks. This genus is quite different from the genus Mergus which includes the Red-breasted Merganser and the Common Merganser, but interestingly does not include the Hooded Merganser. By studying genera (plural of genus) a birdwatcher can begin to understand some of the subtle differences between birds. By noticing that the Hooded Merganser and the Red-breasted Merganser belong to different genera one would want to understand what the difference is between the two birds. (Kingdom, Phylum, Class, Order, Family, Genus, Species)

 Grasslands - "Grassland biomes are large, rolling terrains of grasses, flowers and herbs. Latitude, soil and local climates for the most part determine what kinds of plants grow in a particular grassland. A grassland is a region where the average annual precipitation is great enough to support grasses, and in some areas a few trees. The precipitation is so eratic that drought and fire prevent large forests from growing. Grasses can survive fires because they grow from the bottom instead of the top. Their stems can grow again after being burned off. The soil of most grasslands is also too thin and dry for trees to survive. " (From, Grasslands , done by The West Tisbury School is a K-8 school located on Martha's Vineyard, an island approximately 6 miles off the south coast of Massachusetts. It is part of the Up-Island Regional School District that is presently composed of the towns of Aquinnah, Chilmark & West Tisbury.)

Grinnell, Joseph - (1877 - 1939) American ornithologist who held the job of Director of the Museum of Vertebrate Zoology at the University of California at Berkeley, and specialized in studying the birds of California. Author of The Distribution of the Birds of California (with Miller) and Philosophy of Nature, a posthumous gathering of his essays in 1943 amongst other books. Some of his writing can be viewed in the natural history accounts of these species: Greater Scaup, Band-tailed Pigeon, Black-bellied Plover, Mountain Chickadee, California Thrasher, Scott's Oriole, Cassin's Finch,

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Habitat - Where an organism lives. For some types of birds like the House Sparrow, the habitat is not important. For other species such as the Clapper Rail there are very specific requirements in the type of habitat it can live in. Quite often habitats are very specific to different species in the same family. The Brown Pelican needs salt water while the White Pelican is almost always in fresh water. The American Dipper is usually found in mountainous streams of fast moving water. There are also species that change habitats during a year. The Common Loon spends its non-breeding time mainly in salt water, while it breeds entirely on freshwater lakes. The Wrentit is only found in chaparral habitat, while the American Crow is found in most every habitat. A bird's habitat is different from its range.

Hemiptera - Large order of insects that includes the true bugs.

Herbivorous - Animals that eat primarily plants (i.e., Blue Grouse, White-tailed Ptarmigan)

Heermann, A. L. (1827 - 1865) "Adolphus Lewis Heermann was a surgeon-naturalist in the Army of the United States who worked closely and effectively with Baird on the Pacific Railroad Surveys. Heermann was born about 1827, the son of a doctor in the United States Navy. It is recorded that both he and his brother were ardent naturalists throughout their youths. He was elected to the Philadelphia Academy in 1845 and graduated from the University of Maryland Medical School in 1846." From, Words for Birds by Edward S. Gruson. The Heermann's Gull was named after A. L. Heermann.

Hoffman, Ralph - Author of Birds of the Pacific States; my first field guide to the birds of the Pacific states and a great pleasure to read. Some of his writing can be viewed in the natural history accounts of these species: Gray Flycatcher, Tri-colored Blackbird,

Huxley, Julian S. (1887 – 1975) - (From Wikipedia) "Sir Julian Sorell Huxley, FRS (June 22, 1887 – February 14, 1975) was a British biologist, author, Humanist and internationalist, known for his popularisations of science in books and lectures. He was the first director of UNESCO and was knighted in 1958." Author of The Courtship Habits of the Great Crested Grebe.

Huxley was part of a distinguished family. His brother was the writer Aldous Huxley, and half-brother a fellow biologist and Nobel laureate, Andrew Huxley; his father was writer and editor Leonard Huxley; and his paternal grandfather was biologist T. H. Huxley, famous as a colleague and supporter of Charles Darwin. His maternal grandfather was the academic Tom Arnold, and great-grandfather Thomas Arnold of Rugby School. Some of his writing can be viewed in the natural history accounts of these species: Little Blue Heron,

Hybrid - When two different species mate and have offspring. Their offspring are almost always unable to have their own babies. Part of the decline of the Black Duck is attributed to their hybridizing with Mallards. The same fate is anticipated with the Spotted Owl and the Barred Owl. A hybridization between an American Avocet and a Black-necked Stilt can be seen in this photo. From Introduction to California Birdlife by Jules Evens and Ian Tait: "Hybridization among closely related species confounds the definition of species but also sheds light on the nature of evolution among birds. When closely related, or recently diverged, species of the same genus (congeners) come into contact, hybridization may occur. Most of the species that do interbreed belong to a superspecies complex and though they may interbreed to a limited extent in overlapping portions of their ranges, they are behaviorally isolated. (Pacific-slope and Cordilleran Flycatchers are sympatric in the northern Siskiyou Mountains, but they are isolated by behavioral differences.) Species pairs of California birds that are prone to limited hybridization include: Red-breasted Sapsucker x Red-naped Sapsucker; Townsend's Warbler x Hermit Warbler; Clark x Western Grebe, Nuttall's x Ladder-backed Woodpecker and possibly Nashville x Virginia Warbler. In contrast, Western Gull x