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1 December 2006 Prolonged Incubation of Non-Viable Eggs in the Bearded Vulture Gypaetus barbatus
Antoni Margalida, Joan Bertran
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We present the frequency and duration of prolonged incubation in the Bearded Vulture and test different hypotheses on the possible adaptive significance of this behaviour. The mean and median prolonged incubation lasted 29 and 25 days respectively (n = 10), i.e., 54% and 46% respectively longer than the average incubation period. There was a negative correlation between the duration of prolonged incubation and the egg-laying date: prolonged incubation lasted longer in earlier clutches than in later ones, and territories with many breeding attempts showed short incubation prolongations. On the other hand, no correlation was found between the duration of prolonged incubation and productivity or breeding success. The results suggest that more experienced birds, which occupy higher quality territories and lay their eggs earlier, prolonged their incubation to a greater extent. Although prolonged incubation may constitute an example of adaptive behaviour, the extensive periods documented in some cases do not appear to support this assumption.



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Antoni Margalida and Joan Bertran "Prolonged Incubation of Non-Viable Eggs in the Bearded Vulture Gypaetus barbatus," Acta Ornithologica 41(2), 181-184, (1 December 2006).
Received: 1 June 2006; Accepted: 1 October 2006; Published: 1 December 2006
Bearded Vulture
birds of prey
energy constraints
Gypaetus barbatus
prolonged incubation
unhatchable eggs
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