Passerines, common name for any of the perching birds belonging to the largest avian order, which includes more than 5700 highly diverse species and well over half of all living birds. Passerines are distinguished by four-toed feet, with three toes pointing forward and one large toe pointing backward. They are mostly songbirds with highly developed syrinxes, or vocal organs. Finches, wrens, swallows, nightingales, crows, warblers, vireos, tanagers, and flycatchers are only a few of the many birds in the passerine order.
In quite recent evolutionary times, passerines underwent an explosive adaptive radiation, working into insect- and seed-rich niches of forests and fields. Passerines are highly diverse in body size, ranging from kinglets at about 5 g (0.18 oz) to ravens at about 1400 g (3 lb). Some, such as crossbills, dippers, and swallows have bill, wing, and leg shapes reflecting highly specialized methods of foraging. Others, such as the crows and jays, are generalists.
Recent research illustrates the interdependence of songbirds and trees. Increasing development in the eastern United States and southern Canada is largely responsible for reducing migrant songbird populations. Development leads to an increase in forest edges and a decrease in the large forest areas migrant songbirds require for nesting. Predators—including raccoons, feral cats, and snakes—hunt along forest edges; as forests are fragmented, hunting grounds for these predators increase. Forest edges are also the preferred domain of the parasitic cowbirds that leave their eggs in songbird nests. At the same time, trees are dependent upon songbird populations. The American redstart and the red-eyed vireo play central roles in minimizing populations of insects that destroy trees. The redstart feeds on regal moths and the red-eyed vireo feeds on gypsy moths, both of which are destructive to white oaks.
The largest suborder of the passerines is the songbirds, or oscines, comprising more than 4500 species. Representative of them are the thrushes, whose complexly muscled syrinxes can produce and imitate a great range of notes and rhythms. Passerines of the three much smaller suborders have less complex syrinxes and are often called suboscines.
“Passerine,” Microsoft® Encarta® Online Encyclopedia 2008
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