Ludwigs J.D. & Becker P.H. (2002) The hurdle of recruitment: Influences of arrival date, colony experience and sex in the Common Tern Sterna hirundo. ARDEA 90 (3): 389-399

Most Common Terns return at the age of two years to their natal colony site and recruit after one or more years prospecting. Whereas this general pattern is known, the mechanisms regulating recruitment are poorly understood. This paper reports on Common Terns that were marked as fledglings since 1992 and recorded as prospectors and recruits in 1994-2001 at a colony in Wilhelmshaven, Germany. All birds were marked with transponders, allowing automatic registration of arrival dates. Of native first-time breeders, 57% were three years old, 6% were already breeding by the age of two, and 37% of the birds recruited between four and seven years. Arrival and laying dates of the recruits were delayed by 17 and 19 d, respectively, in comparison to those of the experienced breeders in the colony. Early arrival at the colony site improved recruitment probability, and with every year that a prospecting Common Tern returned to the future breeding colony the arrivals became earlier. This way the late arrivals of prospecting birds are compensated for by colony experience over the years. The age of first breeding was lower in females (3.2 yr) than in males (3.6 yr), despite the fact that recruiting females arrived later in the season than male recruits. We conclude from this that the hurdles to recruitment are higher for male than for female Common Terns. Recruitment without any colony experience at a young age seems to be an indicator of quality; such birds may benefit by more reproductive years compared to conspecifics, which need to invest one or more years in prospecting