Iowa Winter Birds: American Tree Sparrow

The American tree sparrow's name is really misleading.

European settlers named it the American tree sparrow because the chubby bird with a rust-colored cap and eyeline reminded them of the Eurasian tree sparrow, but Spizelloides arborea isn't just American. It does spend its nonbreeding winter seasons in the U.S. and southern Canada, but it head far north to breed in the tundra of northern Canada. Studies have indicated that of the 20 million American tree sparrows, 87 percent spend some part of the year in the U.S.

Their name is also misleading because they are ground birds and not tree birds. They forage for food on the ground, nest on the ground and breed in scrubby areas where trees are sparse or small.

You've probably heard its alarm call.

Like all birds, tree sparrows have a variety of calls. Check out this video in which you can hear its alarm call, a sharp tseet sound that you have probably heard before. In the background you can also hear a musical twitter that is used when feeding or foraging in flocks.

Males also have one- or two-second songs that they sing in late winter. What's interesting is that there are many male song dialects, but each male only sings one dialect, similar to human language.

Sparrows are hard to identify.

Especially for novice birders, sparrows are difficult to identify because of their similarities. American tree sparrows have small bills and long, thin tails in the world of sparrows. They are only about 5.5 inches long, about the size of a house sparrow.

American tree sparrows and chipping sparrows look incredibly similar. American tree sparrows can have a chest spot, seen in the video above, but that is not necessarily a reliable indicator. In the winter, look for a rusty eyeline instead of a black eyeline and a bi-colored bill with a dark upper mandible and a yellow lower mandible, whereas chipping sparrows have a pinkish bill. American tree sparrows also have a rusty patch on the shoulder, whereas the chipping sparrow's shoulder is gray. The American tree sparrow's wing bars are clearly white, and the chipping sparrow's wing bars are a dingier color.

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Chipping sparrow

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American tree sparrow

American tree sparrows' diet changes throughout the year.

In the wintertime, when these birds are in Iowa, they are almost 100 percent vegetarian, eating grasses, sedges, ragweed and other forbs as well as berries and a few insects. They also are frequent visitors to backyard bird feeders where they like black oil and hulled sunflower seeds, nyjer, cracked corn, peanut hearts and millet.

During breeding season, American tree sparrows look for protein-rich foods for their young such as insects, caterpillars, spiders and snails.

Check out more in this winter birds series:
Dark-eyed juncos
Purple finch
Pine siskin