Here in northern Indiana, some of our birds are summer residents, others pass through during migration, and yet others are here only during the coldest time of the year. I like to refer to the latter group as "snowbirds." One of our more abundant snowbirds, pictured below, is just over six inches long and can be identified by its gray face, rusty cap and eyeline, dark "stickpin" on the chest, and distinct white wingbars. This is an American Tree Sparrow (Spizella arborea), a real harbinger of winter in these parts.
One could only expect that a bird referred to as a "tree sparrow" would nest and/or forage in forested areas. You may be surprised, then, to learn that American Tree Sparrows nest on the ground, forage on the ground, and breed at an elevation above which trees are even able to grow. How, then, did this species get its name? As the story goes, early North American settlers were reminded of the Eurasian Tree Sparrow (Passer montanus) when they initially saw our "tree" sparrows, and thus dubbed them American Tree Sparrows without understanding the behavior and habits of the species.
It's no secret that American Tree Sparrows like it cold. They breed and spend the summer only in the extreme northern parts of North America, where the temperature never gets above 50 degrees Farenheit. While in the harsh environment of the arctic tundra, American Tree Sparrows feed almost exclusively on insects; in the winter, however, their diet is comprised of seeds, especially those of Tall Goldenrod (Solidago altissima) and Canada Goldenrod (Solidago canadensis).
This winter, be sure to listen for the beautiful, high-pitched, tinkling "tweedle-eet, tweedle-eet" coming from old-field habitats, and watch for the characteristic ground-scratching underneath your feeders, and you are sure to see one of our hardiest winter residents, the American Tree Sparrow.