When we talk about identifying sparrows and other streaky brownish birds, one of the things we focus on is whether the breast is streaked or unstreaked.
This is a good place to start, as it allows us to divide birds swiftly into two groups, but what then? Or what if the bird is facing away from you? The pattern of streaks on the back can be helpful as well, but we tend to overlook this field mark.
Because all sparrows have at least some streaks on the back, the patterns can’t be sorted yes or no as breast patterns can, but there is more variety in back patterns than in breast patterns. This makes them more complicated but also more useful for identification.
House Sparrow, House Finch, Chipping Sparrow, and Song Sparrow are common species that have distinctly different back patterns. I made the sketches above to illustrate how useful the streaks can be.
House Sparrow’s back is distinctive: two broad pale stripes bracketing a broad dark center stripe. No other common sparrow or finch shows this pattern. It’s a handy clue you can use to identify a group of sparrows on the ground quickly. House Finch, by contrast, is about as indistinctly streaked as a sparrow or finch gets. It has smudgy streaks in shades of gray-brown.
Chipping Sparrow has a two-color palette, with relatively thin, even, dark streaks on a plain brownish ground color, while Song Sparrow has a more complex pattern, essentially tricolored in black, rufous, and buff. The dark centers of the feathers and pale edges create a streaked pattern, but the streaks have a more variegated, “spangled” look than the simple linear marks of Chipping Sparrow.
Take a few extra minutes this month to appreciate the intricate back streaking on the sparrows at your bird feeder. As you develop an understanding of the variation between species, you will gain important additional clues to the birds’ identities.
This article from David Sibley’s “ID Toolkit” column appeared in the January/February 2015 issue of BirdWatching.