Compensating for the costs of polygyny in hen harriers Circus cyaneus |
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Authors: | Stephen M. Redpath Fiona M. Leckie Beatriz Arroyo Arjun Amar Simon J. Thirgood |
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Affiliation: | (1) CEH Banchory, Hill of Brathens, Banchory, Aberdeenshire, AB31 4BW, UK;(2) Instituto de Investigacion en Recursos Cinegeticos, Ronda de Toldeo s/n, 13005 Ciudad Real, Spain;(3) RSPB, The Lodge, Sandy, Bedfordshire, SG19 2DL, UK;(4) Game Conservancy Trust, Crubenmore, Newtonmore, Inverness-shire, PH20 1BE, UK;(5) The Macaulay Institute, Craigibuckler, Aberdeen, AB15 8QH, UK |
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Abstract: | In polygynous species, the adults are faced with a dilemma during chick rearing. Males must decide how to distribute food between their females and food allocation patterns are often highly unequal. In turn, the females that receive less food from males have to decide how much time to invest in additional hunting. If they spend more time hunting, then they leave their young exposed to weather and predators. However, if they stay at the nest, they increase the risk of their chicks starving. One way that birds may compensate for reduced provisioning is by increasing the size of prey caught. We tested this hypothesis by comparing prey deliveries to nests of hen harriers, Circus cyaneus, with females of different breeding status. As expected, male harriers delivered less food items to the nests of polygynous females, and especially their secondary, or β females. However, both sexes were able to compensate by delivering larger items and there was no difference in the overall mass of food delivered to nests. Moreover, females spent a similar amount of time at the nest, irrespective of status, and there were no overall differences in breeding success. Our results show that polygynous female harriers can compensate for the costs of polygyny, but we suggest that their ability to do so will vary according to the abundance of both large prey and predators. |
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Keywords: | Polygyny Provisioning Parental care Harriers Circus cyaneus |
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