Age-specific reproductive performance of Black Grouse Tetrao tetrix females |
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| Authors: | A. Caizergues L.N. Ellison |
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| Affiliation: | 1. Office National de la Chasse et de la Faune Sauvage, CNERA Avifaune Migratrice , La Tour du Valat, Le Sambuc, F‐13200 Arles, France;2. Centre de Recherche de la Tour du Valat, Le Sambuc , F‐13200 Arles, France;3. Centre d'Ecologie Fonctionnelle et Evolutive, Centre National de la Recherche Scientifique , 1919 Route de Mende, F‐34293 Montpellier cedex 5, France jocelyn.champagnon@oncfs.gouv.fr;5. Office National de la Chasse et de la Faune Sauvage, CNERA Avifaune Migratrice , La Tour du Valat, Le Sambuc, F‐13200 Arles, France;6. Aquatic Biology and Chemistry , Kristianstad University , SE‐291 88 Kristianstad, Sweden;7. Centre de Recherche de la Tour du Valat, Le Sambuc , F‐13200 Arles, France |
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| Abstract: | As part of a demographic study of Black Grouse in the southern French Alps, we estimated variations in reproductive parameters in relation to age of females. Both yearlings and adults initiated a clutch, but adults raised about eight times more young (yearlings 0.25 chicks/females, adults 1.85 chicks/female). Yearlings laid significantly fewer eggs and initiated incubation later than older females. Success of nests did not differ between the two age classes, but yearlings tended to re-nest less frequently and exhibited higher chick loss than older females. The lower reproductive success of yearlings was primarily due to their lower ability to raise young. At nest sites, nest concealment, as well as vertical and horizontal structure and density of the vegetation, did not differ between yearling and older females, which is consistent with the similarity in nesting success in the two age classes. Results support the hypothesis that the extent of the difference in number of young raised by yearling and older females increases with predation pressure. |
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| Keywords: | Tetrao |
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