The Field Sparrow, Spizella pusilla, is a year-round resident in North Carolina. Individuals from farther north swell the population here during the winter months. Overall, Field Sparrow numbers have declined markedly in the last 50 years. This decline is believed to be due primarily to loss of habitat. They are not usually found in urban or suburban areas, as they prefer areas with tall grasses, brush, and thorny shrubs. They can be found where prairie-like habitat has been preserved or reintroduced, such as at Horseshoe Farm Nature Preserve, Prairie Ridge Ecostation, and Anderson Point Park in Raleigh. According to the Project Feedersatch website, Field Sparrows will come to feeders for cracked corn, hulled sunflower seeds and millet.
Sparrows can be hard to identify, so here are some characteristics to look for. As their name implies, they are among the smaller sparrows. They are pale and have no streaking on their breasts. You may notice their small pink bill and clear full white eyering. They tend to forage for seeds and insects at ground level or low in the scrubs and grasses, but they will pop up to investigate phishing. During the breeding season they sing, and their song is very easily identified. It is likened to a bouncing ping-pong ball – a trill that rises and speeds up. Click on this link to hear the song.
Field Sparrows build their nests near the ground in clumps of grass or in dense schrubs. They lay 3-5 eggs that are whitish with brownish spots. Eggs are incubated by the female for 10-12 days and the young fledge after about a week. The young birds stay hidden in the tall grass/schrub habitat for at least another week, after which they are able to fly. Two or three broods are often raised each season.
What’s in a name?
The Field Sparrow’s scientific name is Spizella pusilla. Spizella comes from the Ancient Greek word spiza, which was a general term for “finch,” with the Latin diminutive –ella added – and they do look like little finches. The specific name, pusilla, is a Latin adjective meaning “tiny, puny;” pusilla itself originated in ancient times as a diminutive form of pusus, which meant “boy.” So, a tiny little finch. The Scottish-American naturalist Alexander Wilson (the same Wilson after whom a plover, a snipe, a phalarope, a storm-petrel, and a warbler are named) first named the species in 1810, though the genus Spizella wasn’t named until 1832, by Charles Lucien Bonaparte, another naturalist who, incidentally, happened to be Napoleon Bonaparte’s nephew (Bonaparte’s Gull is named for Charles, not his more famous uncle!). The Field Sparrow is considered to have two subspecies: the nominate subspecies, S. p. pusilla, which is found in most of the eastern United States, wintering mostly in the South, and another subspecies, S. p. arenacea, which breeds on the Great Plains and winters in the western Gulf states.
More on the taxonomy of this group of sparrows
The genus Spizella has undergone some reorganization recently. The American Tree Sparrow, formerly Spizella arborea, was long recognized as the oddball of the genus, and its true relationships were a bit mysterious. DNA work published in a 2003 paper by Rebecca Carson and Greg Spicer in Molecular Phylogenetics and Evolution solved the mystery: the “winter chippy,” as the American Tree Sparrow is sometimes known, is actually a relative of the Fox Sparrow, and the American Ornithologists Union recently ratified this finding by booting this species out of Spizella and placing it in a new genus, Spizelloides. The winter chippy’s song sounds like a higher-pitched version of the Fox Sparrow’s song, both being quite complex—in fact, the first time I ever heard a Fox Sparrow singing in the wild, I thought it was a tanager! Another sign of their relationship is that both species have a “stick-pin” mark on their chest. These two species are both hardy birds, with two of the northernmost breeding ranges of all the sparrows.
Another surprising taxonomic finding has to do with the Worthen’s Sparrow (Spizella wortheni), an endangered species found in north-central Mexico. This bird is almost identical to the Field Sparrow, lacking only the rusty ear mark, and the Field and Worthen’s Sparrows were thought to be each other’s closest relatives. The assumption was that perhaps Worthen’s Sparrow had begun as a population of Field Sparrows that was isolated during one of the ice ages. In 2010, however, Ricardo Canales del Castillo and three co-authors published a DNA-based study in Molecular Phylogenetics and Evolution that showed that the two are not sister species after all. Their findings suggested that Worthen’s Sparrow is most closely related to Brewer’s Sparrow (Spizella breweri), a Rocky Mountain bird whose crown isn’t rusty as in the Field and Worthen’s, but instead is brown-streaked. The Field Sparrow came out as the next-closest relative of those two, though. The next-closest relative of those three turned out to be the Black-chinned Sparrow (S. atrogularis) of the Southwest, whose song sounds remarkably like the Field Sparrow’s. Brewer’s Sparrow’s song, however, is more complex, while Worthen’s Sparrow’s song sounds much like a Chipping Sparrow’s (S. passerina). The Chipping Sparrow came out as the most basal member of the genus, meaning that, evolutionarily, its ancestors split off earliest. The second one to split off was the Clay-colored Sparrow (S. pallida), then the Black-chinned Sparrow, then the Field Sparrow, and finally Brewer’s and Worthen’s split off from each other.
Assuming that Canales del Castillo and his co-authors got the phylogeny right, one might consider how the songs evolved. A simple trill, still shown today by the Chipping and Worthen’s Sparrows, was probably the ancestral Spizella song. The Clay-colored Sparrow, going its own evolutionary way, turned the trill into a dry buzz, but the lineage that led to the remaining species kept it more musical. When the Black-chinned Sparrow’s lineage split off, or perhaps before that evolutionary divergence happened, the song changed so that the trill speeds up partway through. In the Field Sparrow’s lineage, the song evolved so that it not only speeds up in the middle, it also usually rises in pitch, sometimes with another trill at a lower pitch added at the end. Worthen’s Sparrow either kept the ancestral Chipping Sparrow-like form or reverted to it. When the Brewer’s Sparrow’s lineage diverged, the song evolved into a series of trills on different pitches. Sometimes, however, a Brewer’s Sparrow will sing a song with only one or two trills, making its song’s relationship to its relatives’ songs more obvious.
Field Sparrow at Mid Pines Road: Bob Oberfelder
Field Sparrow nest: Jeff Beane
Link to song: https://youtu.be/85eERW5jiGQ