SHORT AND LONG-TERM EFFECTS OF VARIATION IN THE BREEDINGENVIRONMENT ON BEHAVIOUR AND FITNESS TRAITS IN ACOLONIAL, CAVITY NESTING RAPTOR

The heterogeneity of breeding environment leads the evolution of different behavioural strategies that individuals undertake to guarantee their fitness and survival. Moreover, the cyclic nature of animal life determines that each set of decision made by individuals during reproduction could severely affect behaviour and fitness traits during their successive stages of life cycle. Among different species that have been studied to investigate these relationships, migratory birds are optimal model species, since the rigid scheduling of their life cycle exacerbates the associations established among breeding environmental variations, fitness and behaviour. In the present thesis, I investigated the possible effects of variation in the breeding environment on fitness and behavioural traits of a colonial, migratory, avian species the lesser kestrel (Falco naumanni), assessing possible effects during two different temporal scales: in the current breeding season (short-term effects) and/or during successive life stages (long-term effects). In the first part, I analysed short-term effects of breeding environmental variations, observing whether nest-site quality and food resource abundancy and distribution could affect fitness and behaviour of lesser kestrel. Firstly, I have investigated the strategy implemented by lesser kestrel during nest-site selection, and whether individual differences in the nest-site preference could affect fitness. Secondly, I have assessed whether food resource abundancy could limit lesser kestrel’s breeding performance and whether the patchy prey distribution in the breeding environment could negatively affect their foraging behaviour and fitness. In the second part, I have investigated whether variation in breeding environment could affect lesser kestrel during successive stages of the life cycle. I therefore analysed whether breeding area continental distribution affects migratory behaviour and strategy of five European populations of lesser kestrel. The overall results reported in this thesis suggested that lesser kestrel suffers variations in the breeding environment that occur during the current breeding season, indeed I have assessed that individuals rely on public information gathered from the environment to choose the most suitable nest-site and to identify optimal foraging areas. Foraging strategies adopted by lesser kestrel during the breeding season have evolved to cope with the heterogeneous prey distribution and to limit intraspecific competition among individuals of the same and different colonies. Moreover, food resource abundancy mediates individual fitness according to parent body condition. Finally, despite the absence of any direct effects of lesser kestrel migratory connectivity on individual fitness, I observed that the continental distribution of the breeding site reflects the location of the non-breeding areas in Africa. This evidence highlighted that European populations remain separated during the African stay and thus are subjected to different abiotic and biotic traits with possible profound effects on population dynamics.