Abstract
For most seasonal organisms, successful reproduction requires synchronising the rearing period of the offspring with the timing of food availability. Individuals must therefore use cues present in the environment to predict the timing of the food peak and organise their reproduction accordingly. In monogamous species sharing parental care, reproductive success also relies on the strong coordination between partners. In this thesis, I examine whether and how two passerine birds, the blue and great tits, use social and environmental cues to orchestrate their reproduction. Females of these species engage in mate selection, but whether their preference for a partner influences their reproductive decisions has not been explored yet, and this constitutes the first research avenue of this thesis. Although breeding pairs must coordinate with each other, they also have to coordinate with their environment. Birds rely on environmental cues to adapt their reproductive timing with the period of food abundance. Since caterpillars, the main food source used by blue and great tits to feed their nestlings, hatch synchronously with tree budburst, tree phenology has been suggested to be a supplementary cue used by birds to predict caterpillar phenology and thus adapt their reproduction accordingly. Furthermore, tree buds emit olfactory alarm signals when they are grazed by caterpillars. A second research line of this thesis thus explores whether and how birds use vegetation development and olfactory signals from buds to coordinate their reproductive activities with their prey phenology. Combining descriptive and experimental approaches, both in captivity and in the field, this thesis sheds light on how seasonal species adapt to a constantly changing world, ingeniously matching their life cycles to environmental fluctuations.