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[From Spring 1994]
Neotropical migrants or neotropical migratory birds are those species that breed in North American and winter in Mexico, Central and South America and the Caribbean. You know many of these as songbirds. They brighten our lives with flashes of color and beautiful song; they announce the coming of spring, after long winters. Many of us actually take them for granted, but this group of birds is in trouble. In the past several years, the alarming downward population trends of many neotropical species has been made known. The culprits are both the loss of wintering ground habitat and habitat fragmentation on the breeding grounds.
International Migratory Bird Week will be celebrated May 9 - 14. This is a time to focus our attention on all migratory birds, with emphasis on the neotropicals. Chincoteague National Wildlife Refuge was created for migratory birds in 1943 and is suitably located on the Atlantic flyway. The refuge is a major stopover and wintering area for waterfowl. Spring migrations of shorebirds are tremendous, with the peak migration of songbirds through the area occurring during April. Prairie warblers, white eyed vireos, red eyed vireos and yellow warblers are abundant during this period.
Migration is a particularly stressful time for birds; therefore, food and shelter take on added importance. Storms can lead to the death of migrants. However, most birds succeed in making the trip if they find stopovers offering rest and food.
Neotropical migrants make up from sixty to eighty percent of all of the breeding birds in the forests of eastern North America. The songbirds in this group play a critical role in the ecosystem both as consumers and as prey. Their breeding range consists of over fifteen million square miles; yet their wintering grounds comprise only two and three tenths million square miles. Deforestation of this winter range has certainly been responsible for a percentage of the decline of many species. Tropical forests are estimated as being lost at a rate of one to three percent a year. Some countries such as Costa Rica and Cuba have lost eighty percent of their original forests.
While this can account for some of the decline of our songbirds, we in North America must bear some responsibility. Prairie fragmentation in North America has caused us to lose numbers of grassland birds such as the bobolink and dickcissel. Fifty-four percent of our wetlands have been drained, filled and converted to other uses. It is possible that the mid-west has lost as much as seventy to ninety-nine percent of its wetlands. Fragmentation of the forests results in birds being forced to nest in small wood lots where they are vulnerable to predators such as skunks, raccoons, jays, grackles, snakes and house pets as well as to the parasitism of cowbirds. Predators thrive on the edge of the woodlands.
Brown-headed cowbirds once favored open country west of the Mississippi, using the open prairie for feeding and social display. As forests were cleared, their range extended. Now they range over the entire United States. They are not nest builders, choosing instead to lay their eggs in the nests of song birds. Cowbirds parasitize more than one hundred and fifty species of bird, most commonly vireos, warblers and flycatchers. Although they depend on other birds to raise their young, they are an extremely successful species, doubling their population in eight years. Forest fragmentation increases the edge habitat where cowbirds like to feed and to seek someone else's home in which to lay their eggs.
As we enjoy the songbirds of spring, let's also consider their plight and support efforts to protect them and their habitats.
Wilma Young,
Refuge Volunteer
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