Canada Warbler (Wilsonia canadensis) Jack Reinoehl
Magee Marsh Wildlife Area, Ottawa Co., OH 5/22/2008 © Darlene Friedman
Nearly the entire population of the Canada (Click to view a comparison of Atlas I to II) Warbler spends the winter in northwestern South America, within a rather narrow this warbler was found throughout the elevational range on the east slope of the northern LP in MBBA II, with greatest Andes. The summer range extends from density in the northern three tiers of counties New York and New England west across the in the LP and in the UP. In MBBA I, there northern Great Lakes and southern Canada were scattered birds found even away from to the Alberta – British Columbia border. the vicinity of Lake Michigan, south almost South of the primary range, small to the state’s southern border. The greatest populations occur in the Appalachians and decrease in numbers for this warbler around the shores of Lake Michigan between MBBA I and MBBA II was in this (Conway 1999). In Michigan, it is found in small southern LP population, which most counties in the northern LP and UP declined by over 50% between atlases. In with decreasing frequency as one moves southern LP counties not adjacent to Lake south. With its clear, vigorous and fast- Michigan, the drop was most pronounced, paced song, this species is likely to be from 24 townships in MBBA I to just seven noticed by those nearby, but it could still be in MBBA II. overlooked due to its low density of population and restricted habitat. This species is found in forest of various types, both deciduous and coniferous. Distribution However, it is not a bird of unbroken forest, In MBBA I, the Canada Warbler was one of preferring wet shrubland, generally four warblers classified as having the characterized by alder and bordering southern edge of its range extending below wetlands of various types (Conway 1999). “the middle of the LP in the east and west” (Brewer 1991). The present range is similar;
© 2011 Kalamazoo Nature Center Canada Warbler (Wilsonia canadensis) Jack Reinoehl
In states to the south of Michigan, the species than for just about any other Canada Warbler is very rare as a nesting passerine. species. In Ohio, the largest population is in the northeast, which has an impressive This species is single-brooded with eggs laid diversity of northern warbler species; some in June and young fledging in late June and of the Appalachian population also occurs in early May (Conway 1999). There were scattered locations in central and southern only 16 confirmed nestings during MBBA Ohio. Habitat preference in Ohio seems II, a result of the density of habitat occupied mostly to be “hemlock forests, especially . . . by the Canada Warbler and its quick nesting where the understory and ground cover are cycle. Fall migration extends from August relatively dense” (Peterjohn and Rice 1991). through the first half of September. In Indiana and Illinois, the very small populations there (Castrale et al. 1998, Abundance and Population Trends Kleen et al. 2004) may be considered as a (Click to view trends from the BBS) continuation of the Lake Michigan Michigan is not the center of abundance for population, the southernmost population of this species. Population density maps the midwest. produced by the BBS based on data from 1994 to 2003 show the greatest numbers to In Ontario and Wisconsin, the southern edge the east and west of Lake Superior from of regular occurrence is almost the same as Minnesota to the Maritime Provinces. in Michigan. In Wisconsin the population, Another area of high density is northwest of according to BBS surveys, has been steady Great Slave Lake, Northwest Territories (Sauer et al. 2008); in Ontario, the (Sauer et al. 2008). In Michigan, the greatest probability of observation decreased population density is in the UP and NLP. somewhat from the first to the second atlas, The maps for MBBA I and MBBA II show but occurs at relatively high density for a that the rate of detection was similar in these species considered “uncommon throughout areas for both atlases. its range” (McLaren 2007). The Canada Warbler population in Michigan Breeding Biology is estimated by Partners In Flight (PIF 2007) The average arrival of the Canada Warbler to be relatively small. Their estimate of in Michigan is during the second week of 12,000 is smaller than that for seemingly May. Individuals are occasionally scarcer species such as Palm and Cape May encountered during the first week of May Warblers, and only a small fraction of but almost never in April. This warbler’s estimates for the commonest warblers. migration regularly extends into early June Population trend maps from the BBS, based in the southern LP and this is one of the on data from 1966 to 2003, showed this more likely of our warblers to be found as a species decreasing in the western UP and non-breeding wanderer during the summer. increasing in the eastern UP and near Lake Hence sightings in the Possible class need to Michigan. In the period encompassing be regarded with more caution for this MBBA I and MBBA II, BBS data showed
© 2011 Kalamazoo Nature Center Canada Warbler (Wilsonia canadensis) Jack Reinoehl constant populations across the state (Sauer Castrale, J.S., E.M. Hopkins, and C.E. et al. 2008). This is generally consistent Keller. 1998. Atlas of Breeding Birds of with results of the atlases, but these indicate Indiana. Indiana Department of Natural a clear decline of this species in the interior Resources, Division of Fish and of the LP, where populations were small Wildlife, Nongame and Endangered even during MBBA I. Wildlife Program. Indianapolis, IN. Conway, C.J. 1999. Canada Warbler Conservation Needs (Wilsonia canadensis). In The Birds of Though the Michigan population of the North America, No. 421 (A. Poole and F. Canada Warbler appears stable, this species Gill, eds.). The Birds of North America, is in decline over much of its range. The Inc., Philadelphia, PA. American Bird Conservancy has placed it on Kleen, V.M., L. Cordle, and R.A. their Yellow List, meaning that it is a Montgomery. 2004. The Illinois declining species (ABC 2010). The greatest Breeding Bird Atlas. Illinois Natural declines are in the northeast. In New York, History Survey. Special Publication No. McGowan and Corwin (2008) suggest that 26. the steep annual decline of 5% may be due McGowan, K.J., and K. Corwin (eds.). 2008. in part to “forest maturation and deer The Second Atlas of Breeding Birds in browse.” They point out however, a lack of New York State. Cornell University similar declines in other warblers occupying Press, Ithaca, NY. similar habitat. This suggests that some of McLaren, I. 2007. In Cadman, M.D., D.A. the decline may be the result of events on Sutherland, G.G. Beck, D. Lepage, and the wintering grounds. In the northern A.R. Couturier (eds.). 2007. Atlas of the Andes region, “habitat loss is proceeding Breeding Birds of Ontario, 2001-2005. rapidly” (Conway 1999). Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Literature Citations Ontario Ministry of Natural Resources, American Bird Conservancy (ABC). 2010. and Ontario Nature. Toronto, Ontario. WatchList Species Account for Canada Partners in Flight (PIF). 2007. PIF Warbler (Wilsonia canadensis). Landbird Population Estimates Available on-line at: Database [web application]. Version
© 2011 Kalamazoo Nature Center Canada Warbler (Wilsonia canadensis) Jack Reinoehl
Survey, Results and Analysis, 1966- 2007. Version 5.15.2008. USGS Patuxent Wildlife Research Center. Laurel, MD.
© 2011 Kalamazoo Nature Center