For the Birds Radio Program: Savannah Sparrow
Laura talks about the bird that produces a soft, dreamy buzz, which is a trademark of lazy summer days. 4:04
(Recording of a Savannah Sparrow)
That soft, dreamy buzz is a trademark of lazy summer days— the song of the Savannah Sparrow. Savannah Sparrows are common to abundant summer birds over most of North America—the only place on the continent where they don’t breed is in the southeastern United States. This is a bit ironic when you consider that this species is named for Savannah, Georgia, where it was first discovered by Alexander Wilson in 1811 but which is one of the few places where it never breeds.
Savannah Sparrows sing all day, even during the heat of the afternoon, but they’re inconspicuous even if they are abundant. And often when people do get a glimpse at one, they mistake it for a Song Sparrow. Since both species can often be found in the same weedy fields, it’s important to learn the differences between them. Song and Savannah Sparrows both have streaked breasts, and in both species the streaking often appears to coalesce into a large central breast spot. Field guides stress the fact that the Song Sparrow has a long, rounded tail while the Savannah Sparrow sports a shorter, notched tail. For some reason most books also mention the fact that Savannah Sparrows generally have pinkish feet–but this doesn’t help much because under most conditions you can’t see their feet anyway, and when you do it doesn’t make any difference because the Song Sparrow has pink feet, too.
I tell the two apart by their faces. The Savannah Sparrow has more streaks and dots on its face, especially on the crown and behind the cheek patch. Also, the Savannah Sparrow often has a diagnostic little yellow mark above the eye, especially an adult in summer. If you notice that mark on a streaky little bird you can be sure you’re looking at a Savannah Sparrow.
There are two ecological races of Savannah Sparrows in the eastern United States, one living in fields, and one in salt marshes. For a long time this race was considered a separate species, called the Ipswich Sparrow. This bird doesn’t have salt glands for excreting excess salt through its bill like an albatross, but it does have a different, unique adaptation for surviving in its salty niche. Its kidneys are able to concentrate salt in the urine to more than four times the salt level in its blood plasma. This is better than twice the concentration attained by most birds–a handy adaptation for hot summer days when all there is is salt water to drink.
For such a small, inconspicuous bird, the Savannah Sparrow is remarkably easy to study in the field. Males sing from a fence post, tall weed, or other conspicuous perch. The only trick is that when alarmed, they don’t always fly to another perch in the straightforward fashion of most birds—they sometimes run for cover on the ground. But after watching them for a few hours it’s a simple matter to map out their individual territories. Ornithologists have learned that Savannah Sparrows have much greater nesting success in large territories—the optimum size seems to be about 600 to 1200 square meters. They need their own piece of land to find enough food for themselves and their young. They eat some weed and grass seeds, but also large quantities of insects—especially beetles.
Savannah Sparrows often set up their territories in the fallow fields beside freeways, undaunted by the noise and pollution. Even at high noon, while the wimps of the bird world are conserving their strength, Savannah Sparrows lisp their pleasing little buzzes, grace notes of tranquility in an otherwise discordant and harsh world.
(Recording of a Savannah Sparrow)
This is Laura Erickson, and this program has been “For the Birds.”