Its brilliant yellow head, together with its loud, rusty-hinge call, make the Yellow-headed Blackbird a conspicuous presence in western wetlands. It breeds in loose colonies and places its nest over water, attached to cattails and reeds. The Yellow-headed Blackbird often nests in the same marsh as the Red-winged Blackbird. The larger Yellow-headed Blackbird is dominant to the Red-winged Blackbird, and displaces the smaller blackbird from the prime nesting spots. The Yellow-headed Blackbird is strongly aggressive toward Marsh Wrens too, probably because of the egg-destroying habits of the wrens. When the Yellow-headed Blackbird finishes breeding and leaves the marsh, Marsh Wrens expand into former blackbird territories. The male Yellow-headed Blackbird defends a small territory of prime nesting reeds. He may attract up to eight females to nest within his area. The male helps feed nestlings, but usually only in the first nest established in his territory. The other females have to feed their young all by themselves.One of the most abundant birds in North America, the Red-winged Blackbird is found in wetlands and agricultural areas across the continent. The black male can hide the brilliant red shoulders or show them off in a dazzling display. The striped female looks strikingly different than the male and could almost be mistaken for a large dark sparrow.Different populations and subspecies of Red-winged Blackbirds vary markedly in size and proportions. An experiment was conducted that moved nestlings between populations and found that the chicks grew up to resemble their foster parents. This study indicated that much of the difference seen between populations is the result of the different environments. The Red-winged Blackbird is a highly polygynous species, with one male having up to 15 different females making nests in his territory. In some populations 90% of territorial males have more than one female. But, from one quarter to up to half of the young in "his" nests do not belong to the territorial male. Instead they have been sired by neighboring males. The male Red-winged Blackbird fiercely defends his territory during the breeding season. He may spend more than a quarter of all the daylight hours in territory defense. He vigorously keeps all other males out of the territory and defends the nests from predators. He will attack much larger animals, including horses and people. The Red-winged Blackbird forms roosting congregations in all months of the year. In the summer it will roost in small numbers at night in the wetlands where it forages and breeds. In winter, it can form huge congregations of several million birds, which congregate in the evening and spread out each morning. Some may travel as far as 80 km (50 mi) between the roosting and feeding sites. It commonly shares its winter roost with other blackbird species and European Starlings.(Cornell Lab of Ornithology. All About Birds (Online)). |
