Monday, March 10, 2014
By HERB WILSON
Sparrows are some of the most challenging birds to identify. Many of them have muted, dark plumages, offering few obvious identification features. Add the secretive nature of many sparrows and clinching an identification can be tough.
The different genera of sparrows usually have a distinctive shape and silhouette, allowing a birder to quickly home in on the right part of the field guide. Today we'll concentrate on the genus Spizella. Members of this genus are small, slim sparrows with long notched tails and a gregarious nature.
The chipping sparrow and the American tree sparrow are the two most common species of the four Spizella in our state. Field sparrows are far more common in the southern third of the state but seem to be expanding northward in their breeding range. Clay-colored sparrows are vagrants that occur annually but uncommonly.
We are about to see the changing of the Spizella guard. American tree sparrows are winter residents in Maine, arriving from their northerly breeding grounds in late October. They depart in early April, northbound with nesting on their minds. They are replaced by chipping sparrows, a common breeder throughout the state that winter in the Southeastern and Gulf Coast states.
For a brief time in April, both species may be present at Maine. These two species are quite similar with the usual unstreaked breast of a Spizella sparrow. Both species have a rufous cap and a strong, dark line through the eye. The chipping sparrow has a sharply defined white stripe (the supercilium) above the eye; that area of the face is gray and less prominent in the American tree sparrow. The bill of the chipping sparrow is a single color (dark in adult breeding birds, pinkish in the non-breeding season) but the American tree sparrow is bicolored with the upper mandible being dark and the lower mandible being light.
The breast of the American tree sparrow is buff-colored contrasting with the gray breast of a chipping sparrow. The upper parts of an American tree sparrow are a more vibrant brown than the dull brown uppersides of the chipping sparrow.
I hope this column will prove timely in allowing you to experience a vocal treat. As the American tree sparrows prepare to migrate, they start to sing their understated, yet glorious, song. The song starts with a few clear notes and then proceeds as a mix of warbled, descending notes. Listen to it at: http://tinyurl.com/bnp9z4d
Hearing the song in Maine is a special treat because we only have a couple weeks before the American tree sparrows are northbound. Give a listen around your feeder during the first two weeks of April.
The common name for the American tree sparrow is a misnomer. This species mostly breeds north of the latitudinal treeline on the Arctic tundra. No trees there. The reason for the common name is that this species is superficially similar to the Eurasian tree sparrow (a relative of the house sparrow), in a different family from the American tree sparrow.
On the breeding grounds, males court females by singing a single song type. Interestingly, males in a local area may share that particular song. Females build a nest on the ground with no assistance from the mate. Four to six eggs are laid and incubated by the female. The male does pitch in with the feeding.
Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at: