WatchList Species Account for Canada Warbler
(Wilsonia canadensis)

Qualifies for the list as a Declining Yellow List Species


Photo: © Laura Erickson

Photo: Laura Erickson,
Binoculars.com

The Canada Warbler breeds in the northeastern U.S. south in the mountains to Georgia and in boreal Canada. Its preferred habitat is cool, moist forests with mixed coniferous and deciduous trees and a thick understory. In the southern mountains it frequents rhododendron thickets, while favoring forested wetlands further to the north and aspen/poplar forests in the boreal parts of its range. During migration it is found in thick understory in parks and in thickets along streams and forest edges. It winters in northern South America.

Though vulnerable to human disturbance of its breeding habitat, it will tolerate at least moderate disturbance. It is apparently sensitive to reduction of understory by deer browse and also to forest fragmentation. It responds positively to changes that increase the density of understory and negatively to those that severely reduce forest canopy.

 

Breeding Bird Survey (BBS) results from 1966 – 2001 indicate that populations have declined at rate of 1.9% per year throughout its breeding range, with the greatest declines in the Northeast, where the draining of forested wetlands and forest fragmentation have eliminated much of its breeding habitat. Degradation of southern mountain forests through acid rain and the spread of the woolly adelgid, which kills Fraser Fir, have also reduced its available habitat.


Protection of forested swamps where this warbler breeds is essential for its conservation in a large part of its range, but since its favored breeding areas are hard to access, it is difficult to monitor populations. The bird probably responds favorably to habitat changes that increase forest understory and negatively to those which reduce the understory.

 

A serious threat to the Canada Warbler is the reduction of habitat on its wintering grounds in the northern Andes, where human population pressure is increasing with an accompanying rapid loss of habitat. More study of its wintering habitats would be beneficial to conservation of the species.