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1 January 2017 Bluebirds Perceive Prey Switching by Cooper's Hawks Across an Urban Gradient and Adjust Reproductive Effort
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Urban-adapting carnivorous predators such as the Cooper's hawk appear to be adjusting their diet in urban areas to mostly include larger-bodied adult birds rather than nest contents, compared to Cooper's hawks in natural areas. If adult prey in urban areas are relatively more threatened by predation relative to their offspring and non-urban adults, then life-history theory predicts contrasting shifts in urban vs. non-urban reproductive behavior and effort. We tested whether urban and non-urban Eastern bluebirds exhibited contrasting reproductive effort consistent with shifts in the relative risk perception of adult vs. nest predation. At urban sites, Eastern bluebirds using nest boxes exposed to broadcasts of Cooper's hawk vocalizations exhibited enhanced reproductive parameters compared to controls, whereas the opposite trend occurred in box-nesting bluebirds at non-urban sites. As predicted by theory, given prey life-stage switching by a dominant predator, increased perception of predation risk from hawks led to opposing reproductive strategies in urban vs. non-urban habitats. Results align with increasing evidence that urban predation pressures, prey risk perception, and reproductive investment patterns are distinct from those of natural habitats.
© 2017 Université Laval
Kristen M. Malone, Amanda C. Powell, Fangyuan Hua and Kathryn E. Sieving "Bluebirds Perceive Prey Switching by Cooper's Hawks Across an Urban Gradient and Adjust Reproductive Effort," Ecoscience 24(1–2), (1 January 2017).
Received: 14 March 2017; Accepted: 19 June 2017; Published: 1 January 2017

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