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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.
The brown-headed cowbird is an obligate brood parasite; it lays its eggs in the nests of other small passerines (perching birds), particularly those that build cup-like nests. The brown-headed cowbird eggs have been documented in nests of at least 220 host species, including hummingbirds and raptors.
Different host species show different responses to their nests being parasitised, with behaviours ranging from accepting and caring for the cowbird eggs, to rejecting the eggs from the nest. [2] As the shiny cowbird is an effective generalist brood parasite, it can be considered the South American counterpart to the brown-headed cowbird.
A shiny cowbird chick (left) being fed by a rufous-collared sparrow Eastern phoebe nest with one brown-headed cowbird egg (at bottom left) Shiny cowbird parasiting masked water tyrant in Brazil. Brood parasitism is a subclass of parasitism and phenomenon and behavioural pattern of animals that rely on others to raise their young.
The screaming cowbird is a specialist brood parasite, predominantly parasitizing the nests of baywings (Agelaioides). [5] [8] [9] [10] In 1874, W H Hudson was first to observe this parasitic relationship when he witnessed what he believed to be baywing chicks morph into screaming cowbird plumage.
The sexes are very different in size; the male is 50 cm (20 in) long and weighs 520 g (18 oz); the smaller female is 38 cm (15 in) long and weighs 230 g (8.1 oz). In total body mass, the males are 100% bigger than the females, which is a 2:1 body-to-mass ratio and makes the Montezuma oropendola one of the most sexually-dimorphic birds in the world.
Although Carolina wrens are fairly common, brood parasitism by the brown-headed cowbird is common, with up to 25% of Carolina wren nests being affected in certain regions such as Oklahoma and Alabama. [3] [17] Cowbird parasitism peaks in April at 41%, and is as low as 8% and 0% in July and August, respectively. Female cowbirds sometimes eject ...
A common species nest that the cuckoo will choose to place its eggs in is the reed warbler. [7] The common cuckoo distinguishes the warbler's nest and will choose what specific nest to brood in depending on the foliage and distance from the nest. [7] The common cuckoo demonstrates the egg tossing behavior when they are just hatchlings. [14]