Black-capped Chickadee. Photo courtesy of Dan Tallman.
As the cold air and snow set in, most birds leave for warmer climes. Even though this weather may make you feel like hibernating, there are plenty of birds to be seen, some of which are visitors from even colder and snowier places than Carleton! Crossbills, siskins, grosbeaks, and redpolls, collectively known as “winter finches” are rare in the Arb during winter. Most years there are only a few reports, but during ‘irruptive’ winters, when the boreal seed crop fails, or in years following ‘bumper crops’ they move south in large numbers to feed on the seeds of pine and spruce. In these years winter finches may be abundant.
Other winter visitors have similarly irruptive food sources that may force them to move south in bad years. Northern shrikes and various species of arctic owls, which prey primarily on small birds and rodents, show up in Central and Southern Minnesota each year, and could show up at Carleton this winter.
Some birds are present in good numbers every year. Juncos and American tree sparrow eat mostly seeds during the winter, but they’re not as picky as other birds, and mostly migrate south to escape the extreme cold of the Arctic. Golden-crowned Kinglets are an interesting case, as it has been calculated that they could not eat enough to maintain their body temperature in typical Minnesota winters. By huddling together and finding creative places to spend the night, like squirrel nests, Golden-crowned Kinglets can survive the winter here, and avoid the perils of migrating longer distances.
But the most common birds are those that stay in the Arboretum year-round. During winter, without the distraction of beautifully painted warblers with unfamiliar songs, it is easier to appreciate the gregariousness of the chickadee, or the colors of cardinals and blue jays. Robins, usually a sign of spring and summer, are present in small numbers in areas where the remnants of last autumn’s berry crop can still support them. Resident barred and great-horned owls are easier to find in the empty canopy and almost continuous dusk of winter, and can be heard calling at night throughout the Upper and Lower Arb, mostly in February and early March. Listen especially for the comical “who-cooks-for-you, who-cooks-for-you-all” of the barred owl. Before the snow has even melted the mating calls of chickadees, cardinals, and nuthatches can be heard throughout the Arb and on campus.
--Owen McMurtrey, for the Cole Student Naturalists