Detrimental effects of ticks Ornithodoros maritimus on the growth of yellow-legged gull Larus michahellis chicks

The effect of tick Ornithodoros (Alectorobius) maritimus larvae on the grow th of Yellow-legged Gull Larus michahellis* chicks was studied at the Medes Islands colony (NE Spain). Within broods, chicks infested by more larvae w eighed less had a poorer body condition and a shorter wing length than thei r less infested siblings measured at a similar age. There were no differenc es in body measurements before tick infestation. Because mass and size of g ull chicks are significant predictors of probability of hedging, the detrim ental effect of O. maritimus larvae on these parameters may affect the bree ding success of Yellow-legged Gulls, and consequently their life-history an d population dynamics.