Canada Warbler
(Cardellina canadensis)

Overview

Summary

© Dan Busby
For additional photos and vocalizations, visit Dendroica. (Link opens in a new window.)

Still fairly abundant and widespread, the Breeding Bird Survey indicates this primarily Canadian-breeding species has undergone a significant long-term, decrease since about 1970. That decrease, which led to the Committee on the Status of Endangered Wildlife in Canada assessment of Threatened in 2008, is thought to be due primarily to loss of breeding and wintering habitat (COSEWIC 2008a). With over 80% of the species' global breeding population, Canada's responsibility for the species is very high. This species has been identified as a priority for conservation and/or stewardship in one or more Bird Conservation Region Strategies in Canada.

Designations

Population status

Population estimate

Distribution maps

• BirdLife International / NatureServe
• Breeding Bird Survey (BBS): Relative Abundance and Breeding Distribution (1993-2012)
• Atlas of the Breeding Birds of Ontario (2001-2005): Breeding evidence

Migration strategy, occurrence

Responsibility for conservation of world population

Conservation and management

The causes of declines in Canada Warbler populations are unclear. However, loss of wintering habitat in South America is likely a factor,  as well as loss and degradation of habitat on the breeding grounds including loss of forested wetlands and changes to the forest structure (e.g., loss of understory; Reitsma et al. 2010). More recently there is a suggestion that declines in Canada Warbler may be related to spruce budworm populations (Sleep et al. 2009) which have been in decline since the mid-1980s. Spruce budworm populations are known to be cyclical (Royama 1984) and can be expected to surge again to high levels in the near future (Royama et al. 2005). However, other studies suggest there is little evidence at the local scale that Canada Warbler responds strongly to budworm infestation (Venier and Holmes 2010). The Canada Warbler International Conservation Initiative is a new partnership that will further investigate the causes of population declines in this species and coordinate conservation efforts throughout its range. For information on the legal status of this species under the Species at Risk Act (SARA) and to view available recovery documents, see the SARA Registry.

Bird conservation region strategies

Environment and Climate Change Canada and partners have developed Bird Conservation Region Strategies in each of Canada’s Bird Conservation Regions (BCRs). In these strategies, selected species are identified as priorities for one or more of the following reasons:

• conservation concerns (i.e., species vulnerable due to population size, distribution, population trend, abundance, or threats)
• stewardship responsibilities (i.e., species that typify the regional avifauna or have a large proportion of their range or population in the sub-region)
• management concerns (i.e., species that require ongoing management because of their socio-economic importance as game species, or because of their impacts on other species or habitats)
• other concerns (i.e., species deemed a priority by regional experts for other reasons than those listed above or because they are listed as species at risk or concern at the provincial level)

Select any of the sub-regions below to view the BCR strategy for additional details.

References

• COSEWIC. 2008a. COSEWIC Assessment and Status Report on the Canada Warbler Wilsonia canadensis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 38 pp. COSEWIC. 2008a. COSEWIC Assessment and Status Report on the Canada Warbler Wilsonia canadensis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 38 pp. (Link)
• Reitsma, L., M. Goodnow, M.T. Hallworth, and C.J. Conway. 2010. Canada Warbler (Wilsonia canadensis), The Birds of North America Online (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York. Reitsma, L., M. Goodnow, M.T. Hallworth, and C.J. Conway. 2010. Canada Warbler (Wilsonia canadensis), The Birds of North America Online (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York. (Link)
• Royama, T. 1984. Population dynamics of the spruce budworm Choristoneura fumiferana. Ecological Monographs 54(4): 429-462.
• Royama, T., W.E. MacKinnon, E.G. Kettela, N.E. Carter and L.K. Hartling. 2005. Analysis of spruce budworm outbreak cycles in New Brunswick, Canada, since 1952. Ecology 86(5): 1212-1224.
• Sleep, D.J.H., M.C. Drever and K.J. Szuba. 2009. Potential Role of Spruce Budworm in Range-Wide Decline of Canada Warbler. Journal of Wildlife Management 73(4):546-555.
• Venier, L.A. and S.B. Holmes. 2010. A review of the interaction between forest birds and eastern spruce budworm. Environmental Reviews 18:191-207. Venier, L.A. and S.B. Holmes. 2010. A review of the interaction between forest birds and eastern spruce budworm. Environmental Reviews 18:191-207. (Link)