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COSEWIC Assessment and Update Status Report on the Cerulean Warbler in Canada

Summary of Status Report

Since the publication of the first status report for the Cerulean Warbler in Canada (McCracken 1993), the Canadian population appears to have experienced a range contraction. However, given the discreet nature of this species, it is difficult to assess how much of an effect this has had on population size. The current best estimate of the Canadian breeding population is 500 to 1000 breeding pairs.

The three dominant limiting factors for this species are continued habitat destruction on breeding and wintering grounds, as well as during migration, continued fragmentation of existing habitats, and environmental degradation (e.g. acid rain). Given what is known about the habitat requirements of this species, these factors will always be limiting, regardless of population size.

However, the largest potential threat to this long-term health of this species is that the basic biology of this species remains poorly documented and understood, which limits our ability to manage and sustain populations of this species, most notably in the areas of mating and social systems, landscape-scale habitat selection, and migration stopover ecology. Given past research successes on this species in Canada, there exists an important opportunity to manage and promote this species before its continental population decreases beyond a critical point.