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Alaskan Trumpeter Swans in a Warming World
Schmidt, J.H., Lindberg, M.S., Johnson, D.S., Conant, B. and King, J. 2009. Evidence of Alaskan trumpeter swan population growth using Bayesian hierarchical models. Journal of Wildlife Management 73: 720-727.

What was done
The authors employed Bayesian hierarchical models to estimate the population size of trumpeter swans (Cygnus buccinator) based on aerial survey data collected by the U.S. Fish and Wildlife Service throughout all known nesting habitats in the entire state of Alaska, which data collections were first made in 1968 and subsequently in 1975 and every five years thereafter through 2005.

What was learned
Schmidt et al. report that "adult swan populations in Alaska increased at an average rate of 5.9% annually and cygnet production increased at 5.3% annually." They say they also found that "cygnet production exhibited higher rates of increase at higher latitudes in later years," which they opined was "a response to warmer spring temperatures."

What it means
The five researchers concluded that "trumpeter swan populations are increasing in Alaska, especially at northern latitudes," stating that their study "represents one of the first to demonstrate a shift in breeding range of a bird possibly due to climate change." Hence, "for trumpeter swans," they say "it appears that breeding range limits in Alaska have expanded," in response to the significant warming experienced there between 1968 and 2005, suggesting once again that warmer is better than colder for earth's biosphere.

Reviewed 14 October 2009