American Tree Sparrow

January 10, 2019

American Tree Sparrow
Spizella arborea

by Helena Ives
Most universities are within a college town or a city these days. And while it must be very exciting to be immersed in those locations when not in classes, I’m glad I got my undergraduate degree in a “cow town.” It was birding between classes at UConn that helped me to broaden the birds I was familiar with. And it’s what brought me to get my first glimpse of the American Tree Sparrow.

This time last year, a relatively chilly January morning, I was walking among the grassy fields of Horsebarn Hill in Storrs and spotted a small group of American Tree Sparrows foraging and loafing in the grasses a bit ahead of me. To those unfamiliar with birds, this species would likely blend in with the background or be glossed over as just another sparrow. But to a birder’s eye, this species perfectly masters a balance between drab coloring and striking streaks of rufus, especially in an already bland winter backdrop. And, as a species that is more abundant in the central United States, American Tree Sparrows are a welcome surprise in Connecticut on a winter birding walk filled with Northern Cardinals, Downy Woodpeckers, and Carolina Wrens.

An Arctic breeder, American Tree Sparrows in Connecticut are confined to the winter months. Their wintering ground is centralized in the northern to central portion of the United States, in Nebraska, Kansas, Iowa and other places with abundant open space and grassy fields. In Connecticut, they’re less common. They prefer areas that are open and have low vegetation, like field and marshes, but also take advantage of backyard bird feeders. Recently in Connecticut, American Tree Sparrows have been frequenting the open grassy fields of the Connecticut Audubon’s Bafflin Sanctuary in Pomfret and of Goodwin State Forest, where I’ve been seeking out the exciting winter birds out of our common bird feeder crowds.

Within their preferred grassland and marshy habitat, American Tree Sparrows can sometimes be hard to spot because of their rufous and drab coloring, but when you focus on them for a moment their features become bolder. Their rufous cap and eyeline contrast starkly with their grey-white breast (with its single dark spot) and belly, creating a more distinct pattern that is typically easy to pick out when they’re among a group of other sparrow species. Their white wing bars, rufous wing patch, and bi-colored bill are unique among most other species that would be found in the same habitat.

Many sparrow species are thought to be abundant. And some, like the Song Sparrow, are. But American Tree Sparrows have had a different experience. The population is estimated to have declined by 53 percent over the past 40 years. While the reason for the decline is uncertain, changes in the landscapes this species relies on has been attributed as a main contributing factor. The wintering grounds of American Tree Sparrows in Connecticut and the northern portion of the United States has seen a dramatic decrease in early successional habitat which are dominated by grasses, low growing shrubs, and saplings.

Especially in Connecticut, efforts to create more of this young forest and grassland habitat has are increasing, which holds promise for American Tree Sparrows and other species that rely on these areas.

A graduate of the University of Connecticut with a degree in wildlife conservation, Helena Ives is a naturalist for the Connecticut DEEP at the Goodwin State Forest and Education Center in Hampton. Previously, she worked for Connecticut Audubon monitoring birds as part of the Audubon Alliance for Coastal Waterbirds.

Photo by Kelly Colgan Azar, Carolinabirds.org