Timing of initial arrival at the breeding site predicts age at first reproduction in a long-lived migratory bird.

In long-lived vertebrates, individuals generally visit potential breeding areas or populations during one or more seasons before reproducing for the first time. During these years of prospecting, they select a future breeding site, colony, or mate and improve various skills and their physical condition to meet the requirements of reproduction. One precondition of successful reproduction is arrival in time on the breeding grounds.