The effect of tick Ornithodoros (Alectorobius) maritimus larvae on the growth of Yellow-legged Gull Larus michahellis* chicks was studied at the Medes Islands col­ ony (NE Spain). Within broods, chicks infested by more larvae weighed less had a poorer body condition and a shorter wing length than their less infested siblings measured at a similar age. There were no differences in body measurements before tick infestation. Because mass and size of gull chicks are significant predictors of probability of fledging, the detrimental effect of 0. maritimus larvae on these param­ eters may affect the breeding success of Yellow-legged Gulls, and consequently their life-history and population dynamics

Peer reviewed