Birds, particularly those that fly, have a high metabolic rate that heightens their sensitivity to their immediate surroundings. As such, they have long served as bellwethers of environmental change. For example, canaries were brought into coal mines in the United Kingdom as recently as 1986 to monitor carbon monoxide and methane because the birds gave clear indications of distress — they stopped singing and fell off their perches — if these noxious gases began to accumulate.
Seasonal temperature variations influence the proportion of short- and long-distance migratory species in European bird communities.  Bird species that migrate only short distances must endure winter and its meager resources, whereas long-distance migratory birds escape to warmer climes. Both short and long-distance migrants benefit from the expanded resources that result from warm and early springs. In a study of birds at 21 sites across Europe, spring temperatures and the number of long-distance migratory species have increased significantly, while winter temperatures and the number of short-distance migratory species have not.  A computer model of bird populations, which incorporates the United Kingdom’s Hadley Centre HadCM3 climate model, predicts that the warming anticipated over the next half-century will favor long-distance migratory bird species to the detriment of short-distance migratory species.
 Lemoine, N., H. C. Schaefer, and K. Bohning-Gaese (2007) Species richness of migratory birds is influenced by global climate change. Global Ecology and Biogeography 16:55-64.
This is an excerpt from the book Global Climate Change: Convergence of Disciplines by Dr. Arnold J. Bloom and taken from UCVerse of the University of California.
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