A Redpoll Winter in New England
Like a gift from Santa Claus, Common Redpoll flocks arrived from the far north at the end of December. Birch, alder and spruce trees across the boreal forest often fail to produce seeds in even-numbered years. Without food to survive the cold winter, redpolls move southward by the tens of thousands. This kind of migration is called an irruption, and we’re in the middle of one here in New England.
During an irruptive migration, flocks of redpolls are usually comprised of fewer than 100 individuals. But occasionally they can balloon to amazing numbers. For example, in March 1941 a birder reported a flock of 3,000 to 4,000 redpolls moving up the Connecticut River valley between Vermont and New Hampshire.
The flock at my feeder has been fluctuating between 30 and 60 individuals for several weeks now and they are eating me out of house and home. Redpolls can store seeds in their diverticula, expandable sections of the esophagus. The diverticula can hold up to 2 grams (about 15% of their body mass) of seeds. Depending on the type of the seeds, this gives them about a quarter of their daily energy needs during the winter cold.
Once they have filled their diverticula, they find a sheltered location to regurgitate, husk and swallow the seeds. Sitting in a sheltered location offers safety from predators, but it also saves significant energy when it is very cold.
It looks like my bird feeders are nearly empty again. Its time for another trip down the snow covered road to the feed store once again!