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Ken Yasukawa

Beloit College
Do nestling red-winged blackbirds "blackmail" their parents?
My students and I have tested the hypothesis that vocal begging by nestling red-winged blackbirds is a form of manipulation ("blackmail") to coerce care from parents by increasing the risk of nest predation. Parents then feed nestlings more than they would otherwise to silence them. We tested four predictions: (1) parents adjust care in response to the risk of nest predation, (2) vocal begging increases the risk of nest predation, (3) nestlings respond to elevated predation risk with increased vocal begging, and (4) parents increase feeding of nestlings in the presence of elevated predation risk. In contrast to these predictions, presentations of model predators have showed that parents respond to a simulated risk of nest predation with reluctance to visit their nests, a playback experiment produced no evidence that nests with begging call playbacks were depredated at higher rates than control nests, nestlings did not increase their vocal begging when the risk of predation was experimentally elevated, and parents were not more likely to feed vocalizing nestlings when the risk of predation was experimentally elevated are under way. Our results do not support the blackmail hypothesis for nestling begging.
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