Even though it is April now and spring is officially here, the windows on the back of our house look out over a field of snow that disappears into the woods and only begins to break up when it reaches the river. In front of the house the snow has all melted, robins stroll the lawn discovering insects in the newly-uncovered dirt and cardinals sing from the lilacs. Our front and back yards are like two different seasons, in the front it is spring, in the back it is still winter. There in the back our trusty little suet feeder attracts more winter-appropriate birds, assemblages of chickadees, nuthatches, titmice and diminutive downy woodpeckers. All of these birds are here year-round, but, in the winter, they form large flocks and, to my eyes, become more obvious – hence my associating them with winter.
I was wondering why downy woodpeckers flock with other birds in winter – when I see them in the summer they tend to be by themselves or with their mate, spiraling their way up a tree trunk or along a branch, probing the bark for insects. An interesting article by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye (Stanford Birds 1988) explains one theory on why they form mixed flocks in winter: “By moving together in a mixed-species flock, birds with the same sorts of diets can avoid areas that have already been searched for food. Individuals in mixed flocks can also learn about new food sources from other species; titmice have been observed to visit the site where a woodpecker was pecking at the bark and to begin pecking in the same place. Finally, by associating with birds of different species that have somewhat different food preferences and foraging techniques, each individual faces less competition than it would in a similar flock of conspecifics.”
In addition to downy woodpeckers, I also get hairy woodpeckers at my suet feeder. These two species of birds have almost identical plumage – black and white checkered bodies with a stripe of white down the back and a bright red patch (males only) on the nape of their neck. The best way to tell these two species apart is by size and beak-to-head ratio. Hairy woodpeckers average around 9 inches in length, the downy woodpecker a mere 6 inches. While the hairy woodpecker looks powerful, the downy looks diminutive. Hairy woodpeckers have a large, powerful beak that is almost as long as its head, while the downy beak is short and stubby, almost delicate-looking. Downy woodpeckers definitely do not spend a lot of time hammering into tree trunks like their huge cousins the pileated woodpeckers (these woodpeckers dig into dead trees in search of carpenter ants).
Downy woodpeckers are the smallest woodpecker in North America. Instead of muscling their way into trees, they locate insect tunnels within a trunk by tapping, then break into the tunnel with their chisel-shaped beak and insert their long sticky tongue that ends in a barb into the tunnel, probing for insects. They can actually skewer an insect (these are often the grubs or larvae of various beetles) and pull it from the tunnel. Downies will also search leaves and twigs for insects, eat seeds and berries and have even been known to drink from oriole and hummingbird feeders. They are fairly versatile and do well with humans – able to thrive in as diverse locations as city parks and suburbs – anywhere there are trees. They are one of the most common birds at any feeder.
I’ve enjoyed their daily visits this winter but expect the snow out back to melt sometime soon and the foraging parties of downies, chickadees and nuthatches to disperse. Just one more signal that winter is over and summer is on the way.
Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at firstname.lastname@example.org. Read more of her Nature News columns online.