Individual activity rates in wintering Eurasian woodcocks: starvation versus predation risk trade-off?

摘要: Wintering birds face a trade-off between starvation and predation risk. In Eurasian woodcocks, Scolopax rusticola, habitat use may reflect this because meadows, where most spend the night, are characterized by higher risk of biomass food (earthworms) than woods, used day. We monitored activity 34 woodcocks fitted with tiltswitch radiotags. Young were more active adults, probably they less efficient at foraging. general, nocturnal was inversely correlated air temperature daylight foraging activity, suggesting some compensatory mechanism, modulated thermoregulatory constraints. Individual patterns differed, we classified according to three main wintering strategies: ‘always’, ‘sometimes’ or ‘never’ visiting fields night. The decision fly night seemed be taken every evening, amount in woods temperature. After feeding rich patch on mild day, did not have going meadows. Conversely, patches fewer resources lower temperatures both, could meet all their energy requirements without (where there always sufficient food) eventually, changing diurnal sites. Therefore, depends how efficiently find forest exploit it optimally during