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The female cowbird may continue to observe this nest after laying eggs. Some bird species have evolved the ability to detect such parasitic eggs, and may reject them by pushing them out of their nests, but the female cowbird has been observed to attack and destroy the remaining eggs of such birds as a consequence, dissuading further removals. [8]
Accepting a cowbird egg and rearing a cowbird chick can be costly to a host species. In the American redstart , nests parasitized by cowbirds were found to have a higher rate of predation, likely due in part to the loud begging calls by the cowbird nestling, but also partly explained by the fact that nests likely to be parasitized are also more ...
One study found 22.5% of baywing eggs were punctured by the screaming cowbird. [11] Screaming cowbirds can distinguish between their eggs and those of other species and laboratory trials have shown that screaming cowbirds will puncture shining cowbird (Molothrus bonariensis) eggs more frequently than their own. [22]
The bronzed cowbird (Molothrus aeneus), once known as the red-eyed cowbird, is a small icterid. They breed from the U.S. states of California, Arizona, New Mexico, Texas, and Louisiana south through Central America to Panama. They tend to be found in farmland, brush, and feedlots.
It is social and commonly seen in small groups. Unlike the "true" cowbirds in the genus Molothrus, this species is not a brood parasite. In contrast, the screaming cowbird is a brood parasite of the grayish baywing, and while adult screaming cowbirds are overall blackish, juvenile screaming cowbirds closely resemble grayish baywings.
The giant cowbird (Molothrus oryzivorus) is a large passerine bird in the New World family Icteridae. It breeds from southern Mexico south to northern Argentina, and on Trinidad and Tobago . It may have relatively recently colonised the latter island.
The pale baywing (Agelaioides fringillarius), formerly known as the pale cowbird, is a species of bird in the family Icteridae. It is currently placed in the genus Agelaioides , but has traditionally been placed in the genus Molothrus .
Other remains have also been found at San Clemente de Térapa in the Mexican state of Sonora, mixed with the remains of extant icterid species such as the red-winged blackbird (Agelaius phoeniceus) and orchard oriole (Icterus spurius). More remains have been found as far south as the Talara Tar Seeps in northwestern Peru. [2] [3] [4]