Population declines in North American birds that migrate to the neotropics.

Abstract

Using data from the North American Breeding Bird Survey, we determined that most neotropical migrant bird species that breed in forests of the eastern United States and Canada have recently (1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987) declined in abundance after a period of stable or increasing populations. Most permanent residents and temperate-zone migrants did not show a general pattern of decrease during this period. Field data from Mexico were used to classify a subset of the neotropical migrants as using forest or scrub habitats during winter. Population declines during 1978-1987 were significantly greater among the forest-wintering species, while populations of scrubwintering species increased. The same subset of neotropical migrants also showed overall declines in forest-breeding species, but no significant differences existed between species breeding in forest and scrub habitats. Neotropical migrant species that primarily use forested habitats in either wintering or breeding areas are declining, but a statistically significant association between habitat and population declines was detected only in the tropics.

Habitat Associations, Relative Abundance, and Species Richness of Autumn Landbird Migrants in Southwestern Idaho

“…Populations of some migratory birds, including both Neotropical migrants and shorter-distance, temperate migrants, have declined during the last few decades (e.g., Robbins et al 1989, DeSante and George 1994, Wang and Finch 1997. Most research addressing causes for these population declines has focused on habitat characteristics and population status on the breeding and wintering grounds (Hutto 1988, Sherry andHolmes 1995).…”

A phantom road experiment reveals traffic noise is an invisible source of habitat degradation

“…For individuals that remain in areas disturbed by loud human activities, noise pollution represents an invisible source of habitat degradation that has been largely ignored: Traffic noise degrades habitat value but leaves no physical signs of change. Stopover habitat loss and degradation have been identified as major contributing factors to migratory songbird declines worldwide (37,38). Migrants are exposed to an unknown risk landscape at stopover sites and must therefore rely heavily on increased vigilance to compensate (39)(40)(41).…”

The conservation implications of site fidelity: A case study involving nearctic-neotropical migrant songbirds wintering in a Costa Rican mangrove

“…Substantial population declines have been reported for nearctic-neotropical migrant landbirds over the past four decades, particularly among forestbreeding species (reviewed in Askins et al, 1990). Plausible links have been drawn between these declines and forest fragmentation in North America (with its associated problems of nest predation and parasitism; Terborgh, 1989), as well as the loss of wintering habitat in M6xico, Central and South America (Robbins et al, 1989). Recognition of the latter as a potential leading factor in these population declines has led to greatly increased efforts to understand various aspects of the ecology of nearctic-neotropical migrants during migration and on their wintering grounds.…”