North American species of tyrant flycatchers
The tyrant flycatchers are a large family of perching birds, containing 367 species, and making up the family Tyrannidae in the order Passeriformes. Tyrant flycatchers only breed in the Americas, from the northern boreal forest of Canada, through the rest of North America, Central America, and to South America as far south as Patagonia. Rarely, individual tyrant flycatchers may occur in coastal Europe, but they would have been blown there by a windstorm.
Species of tyrant flycatchers occur in a great diversity of habitats, ranging from sparsely treed prairies to savannas, and forests and woodlands of all types. Species that occur in strongly seasonal, temperate climates are migratory, spending their non-breeding season in the tropics or subtropics.
The species in the Tyrannidae are a highly variable group. The range of body lengths is from 3-9 in (8-23 cm)—not including the long tail of some species. Their wings are relatively long and pointed in species that pursue their prey in the air, or short and rounded in species that glean arthropods from foliage. The tail is usually square-backed or forked, but is very long in some species.
The head of tyrant flycatchers is relatively large, and the beak is stout, somewhat flattened, and has a hook at the tip of the upper mandible. However, fly-catching species have a relatively large bill, while gleaners have a small, more-pointed beak. The fly-catching species also have stiff bristles, known as rictal bristles, around the base of their mouth. The feet are small and weak, and only used for perching.
The plumage of tyrant flycatchers is typically a rather plain, olive-green, brown, or gray, with a lighter belly. Some species, however, can be quite brightly colored, and may have bright hues of yellow or red. Except for the brighter-colored species, the plumage of male and female birds does not differ.
Tyrant flycatchers typically feed by sitting upright at a well-vantaged, prominent perch, from which they can scan the local environment for flying insects, or for insects or spiders on the ground or on foliage. When likely prey items are observed, they are caught in the beak after a brief sally. Often the bird returns to the same perch. This foraging strategy is known, quite appropriately, as "fly-catching." Almost all of the North American flycatchers fly-catch for their living, but many species of tropical forests glean their prey from foliage and other surfaces. Some species add fruit to their diet, and some of the larger species will prey on mice and small lizards, which are caught on the ground.
Tyrant flycatchers are solitary, and do not form flocks. Tyrant flycatchers are strongly territorial during their breeding season, and some hyper-aggressive species, such as kingbirds, even drive other species away from the proximity of their territory. Tyrant flycatchers have distinctive calls, but the song is not very well developed in most species.
Most species of tyrant flycatchers build cup-shaped nests in trees or shrubs. The clutch size ranges from two to six eggs, with northern species having larger clutches than tropical ones. The eggs are usually incubated by the female. However, the male flycatcher assists with the care and feeding of the young, downy birds.
A total of 31 species of tyrant flycatchers breed regularly in the United States or Canada. All of these are migratory, spending their non-breeding season in Central and South America. Many of the species of tyrant flycatchers are remarkably similar in appearance, and they can be extremely difficult to identify to species, even for experienced birders. This problem is especially acute during the spring and autumn migrations, when the birds are not necessarily in their typical, breeding habitat, and are not singing.
Some of the North American species, and also species elsewhere, are virtually impossible to tell apart by color or morphology. However, the species occupy different sorts of habitats and niches, have different songs, do not interbreed, and are reproductively isolated. These sorts of difficult-to-distinguish species are known to evolutionary biologists as sibling species.
In North America, the best examples of sibling species are two types in the so-called Traill's flycatcher (Empidonax traillii) group, which was shown by detailed field studies to be composed of two, morphologically identical, species. The alder flycatcher (E. alnorum) has a relatively northern distribution, breeding from central Alaska and northern Canada south of the tundra, to southern British Columbia, Michigan, New York, New England, and Appalachia as far south as Maryland. This species breeds in wet alder and willow thickets, bogs, and regenerating burns and cut-overs, and its song sounds like: "fee-bee-ow." The willow flycatcher (E. traillii) breeds further to the south through most of the continental United States, in shrubbery along grassy lake edges and streams, and its song sounds like: "fitz-bew."
Actually, the difficulties do not end with these two sibling species. The alder and willow flycatchers and the Acadian flycatcher (Empidonax virescens) of the eastern United States are the same size, and they have a very similar coloration, as does the almost imperceptibly smaller least flycatcher (E. minimus). As in true sibling species, these four types breed in distinctively different habitats, they have different songs, and they do not interbreed. Biologically, therefore, they are different species, even if frustrated bird-watchers cannot always tell who is what during the migrations of the birds, when they do not occur in typical habitat, and do not usually sing.
Other tyrant flycatchers are considerably easier to deal with. One of the more familiar species over much of the continent is the eastern kingbird (Tyrannus tyrannus), a slaty-backed, white breasted species of open country. The western kingbird (T. verticalis) has a more southwestern distribution.
The great-crested flycatcher (Myiarchus crinitus) occurs in southeastern North America, and is a relatively large, olive-backed bird, with a rufous tail and a yellow belly. The ash-throated flycatcher (M. cinerascens) occurs in the western United States.
The eastern phoebe (Sayornis phoebe) is a small, gray-backed species that ranges widely in eastern North America south of the tundra. This species was named after its call, which sounds like: "fee-bee." Say's phoebe (S. saya) has a more-western distribution. Another species that says its name is the eastern wood peewee (Contopus virens) of southeastern North America, whose call sounds like: "pee-awee."
The olive-sided flycatcher (Nuttallornis borealis) is another widespread species, whose call sounds like: "whip-three-wheers," although most birders actually learn it as: "quick-three-beers."
All of the above species are lively and interesting birds, but they are not strikingly colored or patterned. However, some of the more southern species of tyrant flycatchers are quite gaudy. The scissor-tailed flycatcher (Muscivora forficata) has a light-gray back, with a pink-orange wash on the flanks, and a spectacular, forked tail that is about two-times as long as the bird's body. The kiskadee flycatcher (Pitangus sulphuratus) has a bold, black-and-white pattern on its face, and a bright-yellow belly. However, the most spectacular of the North American species is the vermilion flycatcher (Pyrocephalus rubinus), in which the male is garbed in a dark-charcoal black and tail, but has a fiery, vermilion breast and head.
Ehrlich, P., D. Dobkin, and D. Wheye. The Birders Handbook. New York: Simon and Schuster, 1989.
Farrand, J., ed. The Audubon Society Master Guide to Birding. New York: Knopf, 1983.
Forshaw, Joseph. Encyclopedia of Birds. New York: Academic Press, 1998.
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