Thousands of birds die each spring and fall when they collide with Chicago’s skyscrapers, which lie on a major migration path between Canada and Latin America. But the birds don’t die in vain. Since the 1970s, many of them have been collected from the street by the city’s Field Museum. They were classified and recorded in detail there. This unique and detailed set of data has been a scientific windfall(意外之财), revealing that North American migratory birds appear to be shrinking.
A new study of this data has highlighted an important trend: Birds that have bigger brains, relative to their body size, are not shrinking as much as the smaller-brained members of their species. The study is the first to identify a potential link between cognition and animal response to human-made climate change, according to the researchers from Washington University in St. Louis. “As temperatures warm, body sizes are decreasing,” said Justin Baldwin. “But larger-brained species are declining less strongly than small-brained species.”
Relative brain size is often considered an indicator(指标) of behavioral flexibility in birds, according to the research. The idea is controversial when it’s applied to some other animals, Baldwin said, but it works for birds. “Relative brain size connects with increased learning ability, increased memory, longer lifespans and others,” Baldwin said. “In this case, a bigger-brained species of bird might be able to reduce its exposure to warming temperatures by seeking out habitats with cooler temperatures, for example,” he said.
Birds that had big brains, relative to their bodies, had body-size reductions that were only about one-third of those observed for birds with smaller brains, the study found.
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