Considerable evidence exists that climate change is already affecting bird distributions, arrival, and departure dates of migrants, in addition to breeding dates. Using the National Audubon Society’s Christmas Bird Count data, Price and Root (2005) have shown that, in North America, the northern limits of many bird species are strongly associated with temperature. Twenty-seven of 38 bird species of northeastern forests have shifted their historical ranges northward (Rodenhouse et al. 2009). In addition to shifting their ranges, migratory birds are arriving back at their breeding grounds earlier than in the past. One study found that 20 species of migrating birds were arriving about three weeks earlier in 1994 than they had in 1965 (Price and Root 2005). Evidence shows that some of these birds, such as the tree swallow (Tachycineta bicolor), are laying eggs nine days earlier than they did in the 1950s, in response to warmer spring temperatures (Dunn and Winkler 1999).
Dunn, P.O. and D.W. Winkler. 1999. Climate change effect on breeding date in tree swallows. Proceedings of the Royal Society of London. 266: 2487-2490.
Price, J.T. and T.L. Root. 2005. Potential impacts of climate change on neotropical migrants: management implications. In: Ralph, C.J., and T.D. Rich (eds.). Bird Conservation Implementation and Integration in the Americas. USDA Forest Service, Arcata, CA, 1123-1128.
Raphael, Martin G. 2008. Effects of global climate change on birds. (October 28, 2008). U.S. Department of Agriculture, Forest Service, Climate Change Resource Center.
Rodenhouse, N.L., Christenson, L.M., Parry, D., and L.E. Green. 2009. Climate change effects on native fauna of northeastern forests. Canadian Journal of Forest Research 39:249-263.
