Norma Jean Venable
Orioles, tanangers, purple martins, and wood thrushes are familiar birds to many people who enjoy the lovely songs and colorful plumage. These birds, known as "neotropical migrants," nest in West Virginia and other North American sites but spend up to six winter months in warmer climates of the Americas including Mexico, and Central and South America.
Neotropical migrants, or "neotrops" include more than 150 species of North American birds such as swallows, swifts, flycatchers, vireos, and raptors (birds of prey). Neotropical migrants also include the wood warblers, a colorful group of insect-eating songsters. West Virginia species include the warblers; cerulean, bay-breasted, black and white, Cape May, prairie, chestnut-sided, yellow, hooded, mourning, and blackpoll. In some cases, these birds migrate great distances. The migration route of the blackpoll warbler includes a 1,500-mile over-water flight.
During the summer 60 percent to 80 percent of birds in West Virginia are neotrops. This is a very important group of birds. Brightly colored warblers, vireos, and swallows add brilliant color and song to the summer landscape. In addition, many of these birds -- warblers, flycatchers, and swallows -- are prolific insect-eaters providing natural control of insect populations. Purple martins, for instance, can consume thousands of mosquitoes a day.
During migration, all the neotrops face amazing challenges in the form of scarce food, bad weather, lurking predators, collision with windows, buildings, and other manmade structures, and -- perhaps most serious of all -- loss of habitat. Forest land in all of the Americas has been converted to farmland or urban developments. Tropical rainforests are disappearing, and northern forests are fragmented by development.
Many neotropical birds require large areas of woodland to raise their young. Forest species such as wood warblers need at least 250 acres of forest for successful nesting, since these birds must hatch over 50 percent of their young to maintain population levels. Result? The U.S. Fish and Wildlife Service's Breeding Bird Survey shows that the number of neotropical forest migrants has declined in eastern North America at a rate of 1 to 3 percent a year over the 1978-87 decade. Although this annual rate seems small, if the trend continues many birds could vanish during our lifetime.
Another problem is that forest fragmentation, or breaking up the forest into small patches, forces many of the forest-nesting birds to nest in less preferable smaller forested areas near openings or edges. Studies indicate that nests located within 70 feet of forest edges or clearings suffer the highest predation from cats, raccoons, snakes, and blue jays. These small forest areas where neotrops nest but may not successfully reproduce, are called "sinks." Birds such as the scarlet tanager and wood thrush may be seen around these places, but they may not be raising enough young to replenish themselves.
Another serious problem is that nests near openings are more prone to cowbird predation. Cowbirds, residents of open areas, lay their eggs in the nests of other birds, leaving the cowbird young to be raised by the unsuspecting "host" bird. Often the cowbird young are larger than the warbler or host nestling. The young cowbirds are aggressive and demand the most food from the host parents. The young warblers may starve to death while the cowbird young survive. Cowbird parasitism is a serious threat to many songbirds.
In contrast, nests located in deep woods are less susceptible to cowbird predation. Cowbirds, by the way, used to follow the American bison over the prairies, picking up grubs and worms from dung. It is suspected that cowbirds developed their parasitic habits because of their nomadic behavior of following the roving herds of bison. As the cowbirds moved with the bison, they left their eggs to be hatched and raised by other "home-bound" birds. Bison once lived in West Virginia.
Not all neotrops in West Virginia are birds of the deep woods. Nighthawks, which are related to whip-poor-wills, nest on rooftops in cities and towns. Chimney swifts nest in urban areas. The eastern kingbird and other flycatchers occur around meadows and open areas. The ruby-throated hummingbird can be attracted to backyards.
All these birds need quality habitat: a place to nest, a place to eat, and a place to raise young. A way to help the birds is to maintain parks and forest areas that provide as much food, cover, and space as possible. You can work in your community to:
You can also contact the West Virginia Department of Natural Resources Wildlife Resources Unit for information on "Partners in Flight" a national research and monitoring program directed at helping neotropical migrants. Phone (304) 558-2771, or contact the Operations Center, P.O. Box 67, Elkins, WV 26241-0067.
Access "Partners in Flight" through the Neotropical Migratory Bird Conservation site http://www.nfwf.org/nfwfne.htm