POPULATION ESTIMATES OF BREEDING BLACKBIRDS IN NORTH-DAKOTA, 1967, 1981-1982 AND 1990

Red-winged blackbirds (Agelaius phoeniceus), yellow-headed blackbirds (Xanthocephalus xanthocephalus), and common grackles (Quiscalus quiscu la) were censused on 129 quarter sections in North Dakota during May 1 990. Statewide population estimates of breeding blackbirds in North Da kota were 1,143,000 (SE = 179,000) pairs of red-winged blackbirds, 391 ,000 (SE = 211,000) pairs of yellow-headed blackbirds, and 768,000 (SE = 188,000) pairs of common grackles. Censuses of the same quarter sec tions had been made in 1967 and 1981-1982. Red-winged blackbirds decli ned from 1967 to 1981-1982 and from 1981-1982 to 1990. Number of yello w-headed blackbirds were lower in 1990 than in 1981-1982, but did not differ from 1967. Numbers of common grackles increased from 1967 to 19 81-1982, but did not change from 1981-1982 to 1990. Red-winged blackbi rds (50%) and yellow-headed blackbirds (99%) were most frequently obse rved in wetlands. Residences and farmsteads, including associated vege tation, were important to common grackles with 64% observed in this ha bitat.