Conservation Assessment for Bay-breasted Warbler (Dendroica castanea)

Abstract

This is a draft conservation assessment designed to provide a synopsis of the life history, ecology, and management and conservation concerns of the Bay-breasted Warbler (Dendroica castanea). The primary focus of this conservation assessment is on information relevant to Region 9 of the United States Department of Agriculture Forest Service. The Bay-breasted Warbler is a neotropical migrant that inhabits boreal coniferous forests in a broad band, primarily, across central and eastern Canada. It breeds in northern spruce-fir forests, feeding and nesting in the dense foliage of these conifers. It winters in Panama and northern South America. Males and females are fairly large relative to other members of the genus Dendroica, being 13 to 14 cm long and weighing about 13 g. Bay-breasted Warbler numbers have been reported to dramatically increase and decrease in synchrony with outbreaks and declines of the spruce budworm (Choristoneura fumiferana), a key food item. Its North American breeding distribution is closely correlated with that of spruce and fir in the boreal forest. The greatest threat to the breeding range of the Bay-breasted Warbler is the reduction in the area of old-growth spruce and fir of the boreal forest. Both nesting habitat and food supply (spruce budworm) are at risk when reductions or alterations of these forest areas occurs. Spraying insecticides to control spruce budworm can have direct toxic affect on this Warbler (inhibition of brain acetylcholinesterase activity). Winter habitat degradation and loss is also a threat, as commercial and residential development activity continues to reduce the forested habitats in the tropics. No specific or dedicated management activities have been attempted for the Bay-breasted Warbler in Region 9. If management activities are developed and implemented, they should address ecological sustainability. No past or current conservation activities in Region 9 are known to be relevant to the Bay-breasted Warbler. However, the adoption of an ecosystemcentered forest management perspective within Region 9 would likely help conserve inconspicuous boreal birds such as the Bay-breasted Warbler. No surveying, monitoring or research specific to the Bay-breasted Warbler has occurred or is occurring within the national forests of Region 9, although some generalized bird monitoring is occurring. Modifications to a point-count survey protocol could improve the monitoring of Bay-breasted Warblers in national forests. Considering the limited extent of its habitat within these forests, its migratory behavior and inconspicuous nature, declines in the abundance of Bay-breasted Warblers in Region 9 forests could easily be overlooked.