Neotropical Migrant Songbirds
What is a Neotropical Migrant?
Flight gives birds tremendous mobility and allows them to make dramatic seasonal movements in response to changing seasons and food availability. Many birds do not remain in West Virginia throughout the year. Instead, they migrate south to spend winter months in Central and South America or the Caribbean islands. These birds that breed in North America but migrate to the new-world (neo) tropics are known as Neotropical migrants.
Nationwide, approximately 160 species of birds are considered Neotropical migrants. They occur in every habitat from short-grass prairies to moist forests and represent 14 different families and subfamilies as diverse as hummingbirds, flycatchers, thrushes and warblers. Neotropical migrants have one attribute in common: they all feed on insects to some extent and depend upon them to feed their young.
Threats to Neotropical Migrants:
No one is certain why these Neotropical migrants have declined, but habitat loss and degradation are considered to be primary factors.
Habitat fragmentation breaks large pieces of habitat into smaller ones, and probably is the migrants' greatest threat. Since settlement days, large tracts of prairie, scrub and deciduous forest have been fragmented by crop fields, roads and housing developments.
The open, cup-shaped nests built by most migrants leave eggs and young more vulnerable to predators such as raccoons, snakes, blue jays and crows. Unfortunately for most songbirds, these nest predators do well along forest and prairie edges and their impact on migrant nesting success may be increasing.
Brown-headed cowbirds do not build their own nests, but instead lay eggs in unattended nests of other songbirds. Many forest birds are not adapted to cowbird parasitism and as a result, raise the cowbird young as their own, lowering the number of their young raised. In most cases, the growing cowbird chick outcompetes the host bird's chicks.
Pesticides rarely kill birds or other wildlife directly, but their indirect effects are not well understood. They may reduce birds' abilities to withstand the physiological stresses of migration and certainly reduce insect populations, which in turn may reduce the bird's ability to successfully raise young.
Why Do Some Songbirds Migrate?
Birds migrate primarily to find food. The shortage of insects, rather than cold weather, is the main factor that forces Neotropical migrants to move. Biologists once believed that these migrants originated in the Northern hemisphere and were forced south with the advent of winter. How- ever, most now believe that these birds originated in the tropics and began to move northward each summer to take advantage of the abundant insect population of our northern summer. The longer day length of the temperate summer allows for rapid plant growth and as a consequence, insects become abundant. This abundance draws the tropical birds north.
For the most part, Neotropical migrants are not common backyard birds. Some colorful species, such as the Northern Oriole and Barn Swallow are common along roadsides and around pastures and farms. However, most Neotropical migrants are found in forests and thickets away from human development. Except during migration, many of these species are rarely seen by most people.
The spring return of migrants to West Virginia begins during the first weeks of April, and builds slowly to a peak in late May. In almost any wooded park on a spring morning, you may see small flocks of brightly colored birds foraging voraciously in the trees, often ignoring the birders eager to see them. This brief window of time provides unparalleled opportunities to see otherwise hard-to-see species, yet we are only experiencing a tiny portion of a massive continental wave.
By early June, migration is complete and the birds have set up their summer territories. Within three months they'll complete their nesting cycle and begin their long journey south.
Most Neotropical migrants winter in Central America and the larger islands of the Caribbean. Geography dictates that millions of birds are packed into a small area each winter. While the potential breeding grounds in the U.S. and Canada encompass nearly 25 million square miles, the entire land mass from Mexico to Panama is less than 4 million square miles. More than half of all Neotropical migrants funnel into this small area.
Always on the Move:
Migration often is a long ordeal and one that requires a great deal of energy. Migrant songbirds primarily fly at night and spend the day finding food to build fat reserves for the next leg of their journey.
You Can Help Migratory Birds:
Some of the problems facing migratory songbirds start in our own backyards and communities. Habitat loss and fragmentation from real estate development, agriculture and other activities are the single greatest causes of declining songbird populations in the United States. Many areas now lack the minimum habitat birds use for stopovers along their migration routes.
Protecting these areas requires local action and provides many opportunities for citizen activists to preserve habitat at community and state levels. Identification of high-priority songbird species and habitats, development of conservation strategies, and protection and management of lands through purchase, easement and zoning all can be carried out by citizens working through county and state jurisdictions. Each of us also can do the following:
- Create habitat and provide food sources by planting native trees, shrubs and flowering plants; leave snag trees as potential nesting sites.
- Educate others about the threats migratory songbirds face in two continents.
- Volunteer to participate in monitoring projects such as Breeding Bird Surveys and Migration Counts, which census songbird populations.