Bird Population Trends and Priority Species

For over a decade, there has been growing concern among ornithologists and conservationists about declining trends in many North American bird populations. Initially, the greatest concern was for Neotropical migrants—bird species that breed in North America and migrate to the New World tropics to spend the winter. This group includes species that are dependent on native grassland and shrub habitats as well as those that require large tracts of mature forest for breeding. Evidence of population declines comes primarily from the Breeding Bird Survey (BBS), a program administered by the Biological Resources Division of the U.S. Geological Survey and the Canadian Wildlife Service. The BBS is a bird-counting effort conducted each June by about 2,500 volunteer birders in the United States and Canada.

Several factors could be responsible for the species declines, including loss of habitat on tropical wintering grounds or along migratory corridors, particularly coastlines. But considering that many of the declining species are forest specialists, attention has also focused on habitat changes in North American forests. Although BBS data can show us trends in numbers and distributions, only projects such as BFL examine the habitat needs of a wide array of forest birds. Understanding a species' habitat requirements allows us to determine potential reasons for population declines and to formulate management recommendations that enable us to maintain viable populations.

BFL focuses on studying and conserving a wide range of high-priority forest bird species that belong to numerous taxonomic groups, including hawks, thrushes, woodpeckers, and warblers. These species were selected because they are considered to be of high conservation importance by Partners in Flight (PIF). The PIF prioritization scheme not only looks at population trends, such as BBS data, but also considers the overall vulnerability of a population due to threats on the breeding and wintering grounds, size of the species geographic range, and its relative abundance.

While studying and conserving populations of high-priority species is important, it is also imperative that we sustain and manage forest habitats to support all bird species. By identifying the habitat needs of high-priority species, many of which require large blocks of structurally diverse forest, BFL will in turn benefit common species that have more general habitat requirements and ultimately will help keep common birds common.