Wing length and age, but not tarsus or mass, independently determine spring arrival at breeding territories in a long-distance migrant the Common Whitethroat, Sylvia communis

CapsuleWing length and age independently predicted spring arrival timing in a long-distance migratory warbler, but there was no association with mass or tarsus length.AimsTo test a range of biometric features and other measures of fitness for their importance in determining spring arrival patterns in a long-distance migratory landbird, and to investigate why these features may be important.MethodsFifty-one males with known spring arrival dates were caught and key biometrics were measured at breeding sites across Norfolk, UK, during April and May 2012. Blood samples were also taken in order to consider any effect of infection with blood parasites.ResultsEarly-arriving males were more likely to be adults and to have longer wings. Mass and tarsus length had no significant relationship with arrival timing. Haemosporidian prevalence was low (approximate to 10%) compared to other studies of this species, and so it was not possible to determine the effect of infection on arrival date with confidence.ConclusionsWing length, rather than other measures that simply measure structural body size, is probably important in arrival timing due to either the advantage it confers by increasing flight efficiency or because it reflects past condition during feather growth.