Female great tits (Parus major) reproduce earlier when paired with a male they prefer

Mate choice is a key component of reproductive biology. Females often prefer certain males but do females modulate their reproductive investment depending on whether they are mated with their preferred partner? We investigated this question in great tits (Parus major) where we subjected 36 females to a six-choice mate preference test. Male morphological traits and the female’s own characteristics did not influence the preference females expressed. We did find that females spent significantly more time near more exploratory males. We then paired them with one of the males in aviaries and subsequently monitored their reproductive investment (through measurement of plasma 17β-oestradiol concentrations, first egg date, clutch size, and egg size). Females that were mated with a male for which they had a strong preference laid their first clutch significantly earlier in the season than females paired with a male they less preferred. Our results show that mate preference influences reproductive investment in great tits, thereby linking mate choice to bird reproductive decisions.