Bird of the Month: Brewer’s Sparrow
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
Brewer’s Sparrow
Scientific Name: Spizella breweri
Length: 5.5”
Wingspan: 7.5”
Weight: 0.37 oz (10.5 g)
AOU Alpha Code: BRSP
Brewer’s Sparrow is a bird of the Great Basin, and it is the most populous bird in sagebrush flats and desert shrub habitat in spring and summer.
SAGEBRUSH OBLIGATE
In Washington Brewer’s Sparrow breeds in the shrub-steppe habitat of the Columbia Basin. It is an early spring and fall migrant arriving on the breeding grounds in early to mid-March and departing as early as July. The migration route follows the intermountain west, and the wintering grounds are in similar shrub and sage habitat in the Sonoran and Chihuahuan deserts in the American southwest and northwest Mexico. This sparrow is so acclimated to the dryness of the environment that research has shown it can survive on dry seeds with only 7% moisture for as long as three weeks (Rotenberry, et al; Kaufman).
The nest is a small, open cup of grasses and weeds lined with finer material including animal hair. It is almost always built low in a shrub, never on the ground. Usually, 3-4 pale blue-green eggs with brown spots at the larger end are deposited in the nest. Incubation lasts about two weeks. The roles of the parents in rearing the young are not well known. However, young birds leave the nest in 8-9 days and are still dependent on their parents and not ready for flight (Kaufman). A second brood is possible for some breeding pairs.
DESERT SONGSTER
The plumage of the Brewer’s Sparrow is remarkably understated. It has been described as nondescript, drab, non-committal, and subtle. It is quite plain looking and because of this it is well-suited to its desert surroundings. By contrast, the song of the Brewer’s Sparrow is a lovely linkage of spirited phrases of trills, chips, and buzzes lasting 10 seconds or longer (Rotenberry, et al). A refreshing spring morning filled with songs of several Brewer’s Sparrows is not soon forgotten. You can listen to Brewer’s Sparrows at Macaulay Library .
Brewer’s Sparrow shares the genus Spizella, a little finch, from the Greek spiza, a finch, and the Latin diminutive -ella, with six other North American sparrows. It is named for Thomas Mayo Brewer (1814-1880), a physician, who specialized in the study of bird eggs. John Cassin (1813-1869) named the bird to honor the work of Dr. Brewer. The name for sparrow is from the Anglo-Saxon spearwa, to flutter. The term was originally used to describe any small bird (Holloway).
CONSERVATION NEEDED
Numbers of Brewer’s Sparrows are declining range-wide with losses estimated at between 3 and 6% per year on breeding bird surveys during the 30-period 1966-1996. No state shows increasing trends. Predation by Loggerhead Shrikes, American Kestrels, and Cooper’s and Sharp-shinned Hawks is problematic, but by far the greatest impact on decline has been the fragmentation of shrub-steppe habitat caused by human development and transitioning of the land to agriculture. Currently there are no specific conservation measures in place (Rotenberry, et al).
Where sagebrush habitat is protected for Sage Grouse, Brewer’s Sparrows will also most likely be protected. The species is currently under study as one of six bird species using sagebrush and shrub-steppe habitat in Washington’s Columbia Basin as part of the Sagebrush Songbird Survey sponsored jointly by Audubon Washington and the Washington Department of Fish and Wildlife.
Photo credit Mick Thompson.
References available upon request from amccormick@eastsideaudubon.org.