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The
Brown-headed Cowbird is another bird species that has expanded its range
into Quebec during the last century. Closely associated with domestic cattle,
this bird often feeds on the insects associated with grazing cattle. Unfortunately,
the Brown-headed Cowbird is notorious as a brood parasite. This means that
it never builds a nest but,instead, lays its eggs in the nests of other
species of songbirds. A single cowbird can lay up to 40 eggs per year. This
bird has successfully parasitized the nests of over 144 bird species! Furthermore,
cowbird hatchlings are substantially larger than the host species, making
the chance of survival of the host species low. Considering these conditions,
it is not surprising that the Brown-headed Cowbird has been highly successful
during this century. The Brown-headed Cowbird poses one of the most severe
threats to populations of native songbirds. Although it normally inhabits
open habitats, pastures, and forest edges, increased forest fragmentation
has allowed cowbirds to penetrate forested area, and parasitized nests have
been found more than 4 km from Cowbird habitat. In light of these findings,
adequate protection of songbird populations from parasitism requires the
protection of large tracts of continuous forested land, rather than isolated
patches of forest. |
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