EARLY HEARING DETECTION AND INTERVENTION VIRTUAL CONFERENCE
MARCH 2-5, 2021

(Virtually the same conference, without elevators, airplane tickets, or hotel room keys)

9/28/2018 | 1:25 PM - 1:40 PM | The Nest Survival Lottery | Eccles Conference Center Auditorium

The Nest Survival Lottery

During incubation, females in polygamous birds are faced with trade-offs between self-maintenance and metabolic requirements of the eggs. The female also has to minimize the probability of detection by predators, via nest site selection and nesting behaviour. During 2009-2016 we survived daily number and length of recesses, incubation constancy and the timing of recesses of 70 capercaillie (Tetrao urogallus), 11 black grouse (Tetrao tetrix) and 18 willow ptarmigan (Lagopus lagopus) hens by the use of camera traps. The differences between species were small. Capercaillie, black grouse and willow ptarmigan took 1.84, 2.06 and 2.25 daily recesses averaging 29.10, 25.90 and 26.64 minutes, giving incubation constancies of 0.96, 0.96 and 0.95, respectively. Predators detected nests when flushing females. 31 of 69 (31%) capercaillie nests were robbed the hour after midnight when the incubation constancy was 0.993. During 04:00 – 06:00 capercaillie took most recesses, but females were still sitting 92% of the time on the nest. The difference in nest predation between species cannot be attributed to differences in the observed nesting behaviour. Julian date, number or length of the off-bouts, incubation constancy or interactions between the factors did not explain nest survival in capercaillie. We suggest that variation within hens normal incubation behaviour does not affect the probability of nest predation, and that predators generally detect grouse nests when the hen reveal her nest while escaping the approaching predator. The survival of a grouse nest is a lottery where the female usually has little influence on the outcome.

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Presenters/Authors

Jonas Hagen (), jkghagen@hotmail.no ;
Faculty of Applied Ecology and Agricultural Sciences