Pecking response in Lesser Black-backed Gull chicks Larus fuscus
Ross-Smith, Viola Heather
mesheuropmc: embryonic structures | animal structures
The pecking response of the Lesser Black-backed Gull Larus fuscus ) was investigated. This is a type of innate begging behaviour, whereby chicks peck at the red spot on the parent's bill to induce regurgitation of food. The pecking response in naive chicks was found to be released by a diverse range of stimuli, indicating an initial flexibility in this behaviour. However, chicks' reactions were swiftly adjusted with experience, which may be adaptive in rapidly learning the distinguishing features of their parents and the natal environment, as well as a variety of food items, such that chicks can feed effectively when in competition with siblings. Pecking behaviour was robust to predetermined variation between chicks, mediated by differences in egg and parental quality. Experiments were also conducted on the supernormal pecking response, which involves chicks pecking at a higher rate towards a long, thin, red rod with three terminal white stripes than they do towards the parental bill. Tinbergen and Perdeck (1950), who discovered this phenomenon, suggested that it was an adaptation to the angle at which a newly hatched chick crouching in the nest would first see the parental bill. This was addressed experimentally, along with the hypothesis that supernormal behaviour reflects chicks' innate feeding preferences. Little support was found for Tinbergen and Perdeck's (1950) hypothesis. There was some evidence that supernormal pecking is an adaptation to innate feeding preferences, with chicks choosing food items that shared properties with the supernormal stimulus (the white stripes, the red colour and the thinness). However, experimental evidence could not completely refute an alternative interpretation of supernormal behaviour as a non-adaptive byproduct of the chicks' nervous system (Ramachandran, 2004).