Behavioural and physiological responses to brood parasitism and nest predation in two passerine species

Abstract

Brood parasitism and nest predation are two of the most important selective pressures in birds, particularly in altricial species, which are the species whose nestlings, being born unfeathered, blind and helpless, must be cared by parents. Avian brood parasitism in one of the best examples of a coevolutionary process, where hosts evolve a series of adaptations to counteract and limit the fitness costs imposed by brood parasites. Among these defensive adaptations, the recognition and rejection of the parasitic egg are decisive. Nest predation, on the other hand, is a classic example of agonistic interaction, being the most important force shaping nestlings’ life-history traits since it represents the first cause of mortality for avian offspring. The main aim of this thesis is to expand our knowledge on how these two extremely important selective pressures shape some behavioural and physiological responses in birds This thesis confirms that both brood parasitism and nest predation, through the behavioural and physiological mechanisms that induce, are two decisive selective pressures that strongly shape the evolution of the adaptations in altricial birds. Predation risk is able to trigger an immune response in the organism and this might have important consequences in developing organisms, such as nestlings, as it can alter the normal trade-offs between immunity and the physiological processes of the development. Further we demonstrated the interplay between predation and brood parasitism, offering a new perspective of the forces that may shape the evolution of the anti-parasite defences in host.