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Migration and Stopover Ecology

Migration is widespread among North American birds. Approximately two-thirds of the North American breeding bird species are Nearctic-Neotropical migrants, species that breed in North America and migrate to Mexico, the Caribbean, or Central or South America for the non-breeding season. Although migrant passerines may spend up to a quarter of their year in transit between breeding and wintering grounds, relatively little is known about the biology and behavior of migrants during breaks in migration (stopovers). Interest in the biology of Nearctic-Neotropical migrant species during migration has intensified in the last decade as ornithologists have attempted to understand the entire annual cycle of these species, many of which have shown significant population declines.

Understanding the stopover ecology of migrants is significant because most migrants cannot carry all of the fat needed to fuel the entire migratory journey; therefore, they must periodically interrupt migration to forage and rebuild depleted fat stores. Suitable stopover sites must provide adequate protection from predators as well as an ample food supply to allow migrants to replenish fat reserves rapidly. The availability of suitable stopover sites may pose a serious constraint to the conservation of these species, especially those that have shown declining populations. Understanding how birds use stopover sites could provide valuable information concerning the suitability of sites.

Only a few sites are studying the stopover biology of migrants as they fly between northern breeding sites and southern wintering sites. Even fewer studies have investigated differences in the stopover biology of Nearctic-Neotropical migrants between spring and fall migration, although substantial differences appear to exist (i.e., more frequent and longer stopovers and higher mass gains in the fall on Appledore Island). The goals of the Appledore Island Migration Banding Station are 1) To document the timing of migration by age and sex class during both spring and fall migration; 2) To document the use of Appledore Island, Maine, as a stopover site used by migrating songbirds during spring and fall migration; and 3) To document differences in the behavior of migrants in relation to age, sex, season, and stage of migration.

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