Brewer’s Blackbird, traditionally a western species, started an eastward expansion at the northeast corner of its breeding range in the early 20th century. This expansion carried it 1200 km (over 700 mi) to Michigan and eastern Ontario. This movement may have been facilitated by forest clearance and perhaps also by the species ability to breed and winter in the absence of water (Martin 2002).
DISTRIBUTION. The TBBA database from 1987-1992 shows two possible breeding records for Brewer’s Blackbird in Texas, one apparently in or near the Davis Mountains and one in the northwest Panhandle. Lockwood and Freeman (2004) report a few breeding records for this species in Texas, 2 in Jeff Davis County with 2 other records from the Lubbock area. Apparently Brewer’s Blackbird is a casual breeder in Texas.
This blackbird breeds regularly across southern Canada from British Columbia to Ontario and in the United States from the Pacific Coast east to western New Mexico, Colorado, Wyoming, western South Dakota and east through North Dakota to Michigan. In winter northern populations move south to the Gulf Coast states, Arkansas, Oklahoma, Texas, the desert southwest and mainland Mexico south to the Isthmus of Tehuantepec (Howell and Webb, 1995, Martin 2002).
SEASONAL OCCURRENCE. Wintering Brewer’s Blackbirds have been found in Texas between July 5 and June 8, with most present from late September to late April (Oberholser 1974). In Colorado breeding evidence was obtained from April 19 to August 22 (Melcher 1998).
BREEDING HABITAT. In Colorado, a nearby state where nesting habitat was quantified, 38% of Brewer’s Blackbird nests were in rural/urban habitats, 28% were in riparian vegetation, 18% in shrubland, 11% in grassland habitats and only 5% in pinyon- juniper and ponderosa pine (Melcher 1998).
Brewer’s Blackbirds are very flexible in nest placement; they may breed in single pairs or in loose colonies of 6-30 pairs. Nests may be on the ground in thick vegetative cover, in cliff crevices, in a shrub or a deciduous or coniferous tree as high as 46 m (150 ft) although usually 6-12 m (20-40 ft) above ground. The sturdy nest is built of interlaced twigs, forb stems and grasses, strengthened with mud or cow dung. The nest is lined with rootlets, grass and hair. The outside diameter is 13-15 cm (5-6 in), height 8 cm (3.2 in), inside diameter 7.5 cm (3 in) and the cup depth is 4 cm (1.5 in).
The mean clutch size is about 5 (range 2-7) smooth, slightly glossy, light gray or greenish gray eggs (see Harrison  for photo of markings). The female incubates the eggs for 12-14 days and nestlings leave the nest 12-16 days after hatching. Where the species breeds in colonies, synchronized nesting is common. The socially monogamous pairs raise one brood per year. In areas where the range of this blackbird overlaps that of the larger sized Brown- headed Cowbird (Molothrus ater) subspecies, parasitism rates are as high as 50% (Harrison 1979, Martin 2002).
STATUS. Lockwood and Freeman (2004) describe Brewer’s Blackbird as a common to locally abundant migrant and winter visitor through most of this state. Breeding Bird Survey data from 1252 routes in the United States and Canada produce a statistically significant trend of -1.3% population change per year for the period 1966-2004 (Sauer et al. 2005). This relatively small change, combined with the large and widespread wintering population of Brewer’s Blackbirds in Texas, suggests this species will continue as a member of the Texas avifauna for the foreseeable future. Text by Robert C. Tweit (2006)
Harrison, H. H. 1979. A field guide to western birds’ nests. Houghton Mifflin, Boston, MA.
Howell, S. N. G. and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, New York.
Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M University Press, College Station.
Martin, S.G. 2002. Brewer’s Blackbird (Euphagus cyanocephalus). In The birds of North America, No. 616 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Melcher, C. 1998. Brewer’s Blackbird (Euphagus cyanocephalus). In Colorado breeding bird Atlas, pp. 508-509 (H. E. Kingery, ed.), Colorado Bird Atlas Partnership, Denver.
Oberholser, H. C. 1974. The bird life of Texas, Vol. 2. University of Texas Press, Austin.
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, results and analysis 1966-2004. Version 2005.1. USGS Patuxent Wildlife Research Center, Laurel MD (Web site, http://www.mbr-pwrc.usgs.gov/bbs).