The bounty of birds in Massachusetts, Mitchell said, is noticeably down in the winter. Many do fly south, including almost all the insect-eating birds such as swallows, sparrows, and warblers.
Other birds—such as pine siskins, crossbills, evening grosbeaks, snow buntings, and some blue jays—fly south to Massachusetts from Canada.
Changing Distributions
Birders in Indiana and much of the eastern U.S. commonly associate the arrival of spring with the appearance of robins in their backyards. But Purdue University's Dunning said these birds are no longer a reliable sign of the spring to come. Many stick around all year.
"We have changed the distribution of a number of bird species, because we have modified the environment," he said.
For example, buildings provide increased shelter from the wind, and fruit trees that have been planted throughout suburban landscapes provide food all year. The robin, which lives on fruit in the winter, can now stay put.
Dunning said that many birders in Indiana still believe robins fly south, because they do shift toward out-of-sight habitats along rivers and streams in the early winter.
By the middle of winter, however, the robins have eaten all the berries along the river and are back on lawns eating tree fruits.
So how are folks in the eastern U.S. to know that spring is truly around the corner? Dunning said the appearance of red-winged blackbirds in fields, in marshes, and along roadsides is a more reliable signal.
Red-winged blackbirds stick around much of the eastern U.S. all winter, though they gather in huge flocks around places with lots of food, like grain elevators and agricultural feedlots. "But when the photoperiod starts to change and the days lengthen, the males will leave those flocks and start to claim their territory," he said.
The birds often stake out their territory from power lines or fences, where they can be heard singing a sweet oak-a-lee mating song. Did you hear it today?
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