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Responses of the Great Reed Warbler to Global Warming
Reference
Dyrcz, A. and Halupka, L. 2009. The response of the Great Reed Warbler Acrocephalus arundinaceus to climate change. Journal of Ornithology 150: 39-44.

Background
The Great Reed Warbler breeds in European reedbeds and winters in Africa, and is thus a long-distance migrant, which is the type of bird that according to Bairlein and Winkel (2000), in the words of Dyrcz and Halupka, is expected to "suffer due to climate change."

What was done
The authors examined long-term responses in the breeding performance of Great Reed Warblers -- living on fish ponds near Milicz in southwest Poland -- during various years from 1970 to 2007 (1970-1974, 1981-1984, 1997, and 2004-2007), over which period mean temperatures during the egg-laying months of the species (May-July) rose by a remarkable 2.2C, from 15.3 to 17.5C.

What was learned
Dyrcz and Halupka found a "significant advancement in both earliest and annual [our italics] median first-egg-laying dates" that "correlated with temperature increases early in the season." Latest first-egg-laying dates, on the other hand, remained unchanged, as did several other breeding statistics, including clutch size, nest losses and number of young per nest. Consequently -- and contrary to a Bavarian population of Great Reed Warblers that also advanced its latest first-egg-laying date -- the Polish bird population expanded its breeding season in response to regional warming, whereas the Bavarian birds merely shifted theirs, as documented by Schaefer et al. (2006).

What it means
The two researchers conclude that "the studied population does not benefit from climate warming (as found in Bavaria), but apparently does not suffer," reiterating that "the Great Reed Warbler has adapted well ... by shifting the timing of breeding." Hence, they say the results of their study "do not confirm the prediction of Bairlein and Winkel (2000) that long-distance migrants would suffer due to climate change." In addition, they state that a comparison of their data with that from the Bavarian population "provides evidence that different populations of the same species can adapt in different ways to climate change," noting that "this was also previously found for woodland species," citing the work of Visser et al. (2002) and Sanz (2003).

References
Bairlein, F. and Winkel, W. 2000. Birds and climate change. In: Lozan, J.L., Grassl, H. and Hupfer, P. (Eds.) Climate of the 21st Century: Changes and Risks. Wissenschaftliche Auswertungen, Hamburg, pp. 278-282.

Sanz, J.J. 2003. Large-scale effect of climate change on breeding parameters of pied flycatchers in Western Europe. Ecography 26: 45-50.

Schaefer, T., Lebedur, G., Beier, J. and Leisler, B. 2006. Reproductive responses of two related coexisting songbird species to environmental changes: global warming, competition, and population sizes. Journal of Ornithology 147: 47-56.

Visser, M.E., Silverin, B., Lambrechts, M.M. and Tinbergen, J.M. 2002. No evidence for tree phenology as a cue for the timing of reproduction in tits Parus spp. Avian Science 2: 1-10.

Reviewed 18 February 2009