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From blooming to breeding, the lifecycle of plants and animals are closely tied to seasonal variations in climate. In fall, shorter, cooler days stimulate the onset of fall colors and eventual fall. In spring, following snow-melt, warm, wet nights herald the mating rituals of peepers.
Birds and bears also take their cues from nature, knowing when to emerge from hibernation or when it’s time to migrate north. And something interesting is happening with our feathered friends.
Throughout the eastern United States, several studies show that birds are arriving earlier in the spring. One study recorded tree swallows arriving nearly a month and a half earlier than they did 80 years ago. Can these birds sense global warming?
Birds that winter in the tropics gauge their migration back north based on changes in day length, which stimulates their breeding hormones and the urge to return to their breeding grounds. But how can they sense warmer springtime temperatures when they are thousands of miles away from home?
“A lot of the hypotheses out there is that the timing of, say, arriving to your breeding season for a migratory bird, is presumably tied to sort of match the peak demand for food for your offspring with peak availability of resources that you need to feed them,” says Dr. Ken Schmidt of Texas Tech University.
We should look at the arrival of catbirds, orioles, and robins as a sensitive index of changes in our environment.
Birds have worked out their public debate about global warming. And the early bird gets the worm.
Photo, taken September 23, 2011, courtesy of Costanavarino via Flickr.