This is a very important group of birds. Brightly colored warblers, vireos, and swallows add brilliant color and song to the summer landscape. Purple martins, for instance, can consume thousands of mosquitoes a day. 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. 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.