The Brown-headed Cowbird is a small stocky blackbird that exhibits an interesting way of raising its young. While females of other bird species take charge in building the nest, female Brown-headed Cowbirds focus into egg production, laying more than three dozen in just one summer.
They utilize the nests constructed by other birds and lay their own eggs there. They abandon their young to foster parents, even if it comes at the expense of the host’s own young. Before, the breeding range of Brown-headed Cowbirds is exclusive to the open grasslands of middle North America. However, as humans gradually built towns and cleared woods, the populations of the species have dramatically increased.
The Brown-headed Cowbird has a generally small body which, when compared with most other blackbirds, has a shorter tail and thicker head. Its bill is uniquely shaped, being sorter and thicker-based compared to that of other blackbirds.
The male has a glossy, black body and a rich brown head that looks blackish when hit by poor light or at a distance. The female, on the other hand, has a dull brown plumage with lightly colored streaks on the belly and a dark eye. The head and underparts are noticeably lighter compared to the other parts of the body.
The males are slightly larger compared to females.
Distribution and Habitat
The preferred habitat locations of these birds are forest edges, riparian zones, thickets, prairies, fields, meadows, lawns, cattail marshes, pastures, orchards and suburban areas, and grasslands with low and scattered trees.
They are commonly observed along the edges of closed, forested areas in the morning. In the afternoon, they would forage in open habitats like prairies. When they are not displaying or feeding on the ground, they are commonly observed perching high on prominent tree branches.
They usually avoid forests. As a matter of fact, the development and fragmentation of forest areas in the eastern U.S. paved watt for the expansion of the bird’s population to the east.
Their diet primarily consists of seeds from grasses and weeds, as well as some crop grains. Insects like grasshoppers and beetles constitute about 25 percent of their diet, giving them the protein and calcium supply that they need from laying so many eggs. On top of that, they also eat snail shells and eggs that they have stolen from the nests that they have visited.
They are social animals. They would feed on the ground in numbers, alongside other bird species. The males would flock on lawns for courtship display. And the females would prowl woodlands and edges, searching for nests where they could lay their eggs. During winter, they would flock in numbers to approximately 100,000 birds.
They are also very noisy animals, producing different sounds of clicks, whistles, and chatter-like calls, on top of their flowing, gurgling song. Males would raise their back and chest feathers when they sing. And aside from that, they would also lift their wings and spread their tail feathers, and then bow forward. They fly directly with rapid, constant wingbeats.
The bird is labeled as North America’s most common “brood parasite”, mainly because it does not create its own nest, and instead lays her eggs in the nests of other bird species. On top of that, the host bird raises the young cowbirds. They are known to lay eggs in more than 220 species of birds.
According to some studies, they choose nests that already have some eggs that are not their own. These include Red-winged Blackbird nests, dome-shaped Ovenbird nests on the forest floor, and cup nests in shrubs and treetops. The clutch size is approximately 1-7 eggs. The incubation period for these eggs runs for 10-12 days, while the nesting period would range from 8-13 days. Upon hatching, the young cowbirds are born naked, clumsy, with their eyes closed.
Currently, Brown-headed Cowbirds are widespread across most regions of North America. However, according to the North American Breeding Bird Survey, there has been a recorded decline in the bird’s population between 1966-2010. The estimated global breeding population of the species is 120 million, with 14 percent being native to Canada, 77 percent spending some parts of the year in the United States, and 31 percent in Mexico, respectively.
The bird is classified under the ‘Least Concern’ category of the IUCN. It rates at 7 out of 20 on the Continental Concern Score and is not included in the 2012 Watch List.