Esempi
We observed live female cowbirds at sparrow nests on 12 occasions; 11 of these were laying bouts.
While female cowbirds don't sing, male cowbirds belt out a small repertory of songs, each one less than a second long.
This fracturing allows birds of the forest edge, such as cowbirds and blue jays, to parasitize and prey upon the thrushes.
The only characteristic that separated parasitic cowbirds from their nonparasitic relatives was an increase in eggshell thickness.
In British Columbia, nearly 25% of Veery nests found had been parasitized by cowbirds .
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