Yellow-headed Blackbird Life History

Habitat

Yellow-headed Blackbirds breed in wetlands in prairies, mountain meadows, quaking aspen parklands, and shallow areas of marshes, ponds, and rivers. They nest in cattails, bulrushes, or reeds, often alongside nesting Red-winged Blackbirds. To forage, they may move to surrounding grasslands, croplands, or savanna. In winter, Yellow-headed Blackbirds join up by the thousands into large flocks and forage in crop fields, ranchlands, and farmyards from Arizona, New Mexico, and Texas through much of Mexico. The northernmost wintering populations are mostly males, while the southern ones are mostly females. Back to top

Food

Yellow-headed Blackbirds eat mostly insects in summer and seeds the rest of the year. They catch aquatic insects at the water’s surface, including beetles, grasshoppers, dragonflies, caterpillars, flies, ants, and spiders. Outside of the breeding season they forage in uplands, eating grains and weed seeds. They form “rolling” flocks in farm fields, with individuals continually taking flight at the rear of the flock and landing at the front lines to feed. After establishing a foraging site, a flock will return to the same area repeatedly for several days. The blackbirds probe into soft ground and spread their bills to open up leaf sheaths or enlarge holes. They also flip over stones to unearth food. Back to top

Nesting

Nest Placement

The female chooses a nest site within a male’s territory, always picking a spot that overhangs the water. She affixes the nest to live or dead vegetation—usually cattails, bulrushes, or reeds, but sometimes willows, tamarisk, or wild rice.

Nest Description

The female builds the nest by herself. She weaves long strands of wet vegetation, collected from the surface of the water, around 4–5 upright stems. She adds more strands and more supports, and then an outer wall and an inner cup of the same materials. The outside of the nest is 5–6 inches across and about the same height, while the inside measures about 3 inches across and 2.5 inches deep.

Nesting Facts

Behavior

Males establish territories in deeper-water areas of marshes, often among cattails and bulrushes. Each breeding male attracts a harem of up to eight females that nest within his territory, which he defends from other males. This arrangement means that some males don’t have any mates at all, particularly younger ones. Second-year males usually don’t even secure a territory for themselves, and become “floaters” with no fixed place in the marsh. In some cases breeding birds forage only within their territory, but in other instances breeding is loosely colonial, with birds finding food outside of their own territories. Females defend a small area around the nest and frequently mate with males from neighboring territories when their own mate is absent. Yellow-headed Blackbirds seem to preferentially nest and forage near Forster’s Terns when possible, cooperating with the terns to mob predators or give alarm calls. Yellow-headed Blackbirds displace smaller Red-winged Blackbirds and Marsh Wrens from prime nesting spots in a marsh. Their nest predators include gulls, magpies, Common Grackles, American Bitterns, American Coot, Marsh Wrens, rails, bull snakes, garter snakes, blue racers, mink, red foxes, raccoons, deer mice, and striped skunks. Back to top

Conservation

Yellow-headed Blackbirds are numerous, and their populations are relatively stable in the long term, though they fluctuate considerably from year to year depending on wetland conditions, rainfall, and droughts. The North American Breeding Bird Survey found that this species may have experienced a small decline between 1966 and 2019. Partners in Flight estimates a global breeding population of 11 million and rates them 9 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Yellow-headed Blackbirds appear to be in no danger as long as their habitat remains intact. But because they breed only in wetlands, drainage projects can be a threat (though it tends to affect shallower wetlands more than the larger and deeper wetlands where these blackbirds tend to nest). On the other hand, new fields of corn, sunflower, and small grains have created a vast food supply for the birds outside of the breeding season, probably increasingly the survival rate of fledged young. Because of their diet and habitat choice, Yellow-headed Blackbirds can suffer from exposure to herbicides and pesticides, when the birds eat insects or grain treated or crop-dusted with pesticides, or when farmers use toxic baits or sprays directly against the Yellow-headed Blackbirds themselves. Measures taken to protect crops also include trapping, netting, shooting, and hazing the birds with aircraft.

Credits

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

Twedt, Daniel J. and Richard D. Crawford. (1995). Yellow-headed Blackbird (Xanthocephalus xanthocephalus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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