Do birds behave in order to avoid disclosing their nest site?

Abstract

Aims We tested whether solitary breeders behave in the presence of a predator in order to avoid disclosing their nest site in: hole-nesting Pied Flycatcher Ficedula hypoleuca, shrub-nesting Blackcap Sylvia atricapilla and ground-nesting Meadow Pipit Anthus pratensis. Methods The behaviour of parents in response to two types of predator model (visually oriented Corvid birds and olfactory oriented Mustelid mammals) placed sequentially at 40, 5 and 1 m distance from the nest was recorded from a shelter. Results The hypothesis was supported in open-nesting species (Meadow Pipit and Blackcap), as parents did not approach the nest in the presence of a predator. In the hole-nesting Pied Flycatcher the parents disclosed the nest site in most cases (by entering the nest). The intensity of alarm calling increased with decreasing distance of a predator from the nest in all species except Meadow Pipit in the presence of Raven Corvus corax models. The intensity of attacking changed only in Meadow Pipit with decreasing distance of Stoat Mustela erminea from the nest. Conclusion The results showed that anti-predator behaviour was species-specific, depending on type of predator, habitat and nest inaccessibility. Methods Between 1994 and 1998, 342 birds were ringed as fledglings. From capture–recapture data, annual local survival and the proportion of first-year birds returning to their natal area were computed. Results The annual survival probabilities of adult and first-year birds were constant during the study period (0.67 and 0.57, respectively). A high proportion (0.72) of birds ringed as fledglings returned to their natal area after one year. Of these, an estimated 53% bred in that first year. Local first-year survival is higher in La Crau than other areas in Spain. Conclusion The high local survival rate, the product of survival and philopatry, might be responsible for the positive trend of the population. A peculiar aspect of the La Crau population is that ground nests have been increasingly common since the 1990s despite a higher risk of breeding failure. © 2003 British Trust for Ornithology.