Data from: Prenatal cues of predation risk modulate the lasting effects of postnatal predator exposure in gull chicks.

Prenatal environmental cues can affect embryo development to produce suitable phenotypes that match the expected conditions after birth. In gulls, parental alarm calls during incubation affect postnatal antipredator behaviour, but how chicks integrate reliable prenatal and postnatal information and how this influences their development and viability remain unclear. In this study, we performed a match/mismatch experiment in which we manipulated acoustic cues of predator presence during embryonic development (adult alarm calls vs. colony noise) and simulated predator intrusions during nestling period (mink vs. rabbit decoy) in yellow-legged gulls (<i>Larus michahellis</i>). Our results show that embryonic exposure to predator cues alters the antipredator responses of chicks in early postnatal life as indicated by increased tonic immobility. Chicks exposed to adult alarm calls also displayed rapid crouching behaviour, but only in the absence of predators during the postnatal period. Chicks exposed to postnatal predator presence showed less frequent begging vocalizations. The chicks experiencing mismatched prenatal and postnatal cues of predator presence showed smaller skeletal size and greater genomic damage at fledging, compared to those developed in matched environments. Our results highlight the importance of the late embryonic stage in shaping phenotypic outcomes, with fitness consequences depending on alignment with the postnatal environment.