Embryonic and neonatal vocal elicitation of parental brooding and feeding responses in american white pelicans

Abstract

Calls uttered by late-stage embryonic and neonatal American white pelicans, Pelecanus erythrorhynchos, and parental responses to them were observed during natural parent-offspring interactions and during playback experiments. Observations were all made during the hatching period, when the two-egg clutch consisted of various combinations of unpipped or pipped eggs and newly hatched chicks. From pipping onwards, embryos and neonates uttered short harsh squawks, especially when nest contents were exposed to ambient temperatures. Squawks elicited parental brooding responses that were characterized by foot shuffling over the nest, sometimes in association with pushing an egg or chick back towards the centre of the nest. Brooding responses usually ended with the parent resettling over the nest contents. Brooding response frequency increased with the number of squawks uttered per bout of calling, and was the usual response given to playbacks of squawk calls. After hatching, neonates also began to give a distinctive begging call. Long sequences of begging elicited a characteristic parental feeding posture accompanied by feeding. Parental feeding postures, but not actual feedings, were elicited by 1-min playbacks of begging calls. The data indicate that late-stage embryos and neonatal pelicans utter distinctively different calls for thermoregulatory and nutritional needs, and that parents respond appropriately with brooding or feeding responses designed to ameliorate these needs.