Early American naturalist William Bartram referred to this issue’s species as a Reed Sparrow. Well, that is certainly close. After all, there are reeds in swamps. In 1811, however, when Alexander Wilson described the bird for his American Ornithology, he decided to call it Swamp Sparrow. That makes better sense. Think of all the Swamp Sparrows you have ever seen and then try to remember how many weren’t in swamps.
OK. OK. I know that someone talked about having one at his feeder a while ago. And, I have seen them in open fields that didn’t seem all that wet. But, generally, if there isn’t any water, there isn’t any Swamp Sparrow. I have noticed this when Bill Ellis and I do counts at the Union Mills Wetlands along Brown Road. When the wetlands dry up, the Swamp Sparrows seem to disappear.
John Eastman, in his Birds of Lake, Pond, and Marsh adds another element to the name game. He maintains that Swamp Sparrows more typically reside in open marshland than in swampland. So, should we call them Marsh Sparrows?
The main habitat requirements listed by Eastman include shallow, standing water, low dense (but not uniformly so) cover like sedges, grasses, and cattails, and some elevated perches. Ah, home sweet home!
This is the kind of place that two so inclined Swamp Sparrows can build a nest and raise a family. Monogamy tends to be only seasonal, however. Spring migration peaks in April. Males arrive on territory between one and three weeks before the females. The males are more particular about returning to the same territory they had defended the year previous. The females aren’t. That is why new couples are more likely to form each year.
Breeding territories vary from less than an acre to almost 1 1/2 acres. It all depends on how good the habitat is. If conditions are really favorable to nesting, swamp sparrows may almost be considered colonial with as many as 15 nests per acre.
Not much is really known about the pairing process. Nesting usually begins in May. The male may bring the nest material, but the female decides where the nest is to be constructed and then does it all herself. Usually, the site selected is about a foot above water, although occasionally, a nest may also be built on the ground. Its outside diameter is around 4 inches. Coarse sedges and grasses may be used, but it is then lined with finer plant material.
Four to five eggs are laid. These are green with heavy brown spotting. The female does all the incubation with the male providing meals. This can take anywhere from 12 to 14 days. Once the eggs hatch, both parents feed the young. After they fledge in 9 to 11 days, the female may continue to feed them for another couple of weeks. (Some mothers just can’t let go.) Even then, the family will continue to hang out together for some time.
During the breeding season, 88% of a Swamp Sparrow’s diet is made up of insects. Dragonflies, damselflies, beetles, crickets, ants, bees, aphids, grasshoppers, and caterpillars may be on the menu. Then, as the young birds fledge, Swamp Sparrows start eating more seeds until these make up to 84%-97% of their diet. They might eat the seeds of sedges, smartweeds, vervains, docks, panic grass, etc. Blueberries are also eaten.
Some Swamp Sparrows remain in the southern portions of their breeding range throughout the winter. The species frequently turns up on the CCBC Mid-Winter Count. Others may migrate as far as Mexico. This fall migration is a much more protracted affair than that of the Spring. It usually begins in August, peaking in late September and October. They frequently stop on their way south to rest for a week here and there in areas with good feeding opportunities. The birds we see here in Winter are probably birds from farther North that have migrated south, replacing summer residents.
Like the males that tend to return to the same territories each Spring, Winter philopatry is also common. Small flocks of 6 – 10 birds may feed together. At night, 50 – 60 birds may roost in the same area. Spring migration begins again in mid-March.
David Sibley describes the song of the Swamp Sparrow as “a slow, simple, musical trill chinga, chinga, chinga…fading at the end.” John Eastman thinks it is more like “weet-weet-weet-weet-weet”, resembling the sound of a squeaky wagon wheel. You can decide for yourself. Their call is easier to describe. It is a nice hard “chip”.
Because of their specific habitat requirements, the Swamp Sparrow has few competitors. Song Sparrows prefer to nest where it is a bit drier. Marsh Wrens and Common Yellowthroats may check a Swamp Sparrow’s territory out, but they will almost always be sent packing.
Parasitism of nests by brown-headed cowbirds is common and flooding can present problems for the Swamp Sparrow. Eggs and young may also be lost to predators such as Blue Jays, Common Grackles, Minks, Short-tailed Weasels, Voles, Raccoons, Garter Snakes and Water Snakes. Having avoided all of these, Swamp Sparrows may live for at least six years.
Swamp Sparrows have been described as appearing rather “chunky”. This would be politically incorrect, however, so I will not dwell on it. Overall, the birds have a rusty color to them, with a reddish cap, white throat, and grayish underparts.
The juveniles have less distinct markings and striped crowns as in the photo.