Influence of Chicks and Food Quality on Food Calling in Broody Domestic Hens

The aim of this study was to understand the relationship between production of food calls by maternal hens and both food quality and social context. Nineteen broody hens were tested in twenty experiments combining four different food contexts with five social situations in which they could receive different levels of stimuli from their chicks. Results revealed that the food call rates of broody hens were positively correlated with food quality (or motivational state with regard to food). They were also influenced by the caller's social context: presence of chicks, behaviour of chicks and separation from chicks modified food call production. These results are therefore consistent with previous reports on food calling by cockerels.

Asynchronous hatching and sibling competition in western grebes

Observations of western grebe broods during the 3–4 day period of asynchronous hatching revealed brief but intense bouts of pecking occurring between siblings. Feeding experiments conducted on two live-captured pairs and their newly hatched broods showed that older chicks suppressed the responses of their younger siblings to playbacks of the parental food call. Subordinate chicks that emerged from the parent's back feathers and begged simultaneously with their older siblings usually were pecked, and soon refrained from emerging until the older sibling was satiated. Control experiments that involved separating the two chicks and placing one on each of the parents eliminated suppression by the dominant chick. Possibly, asynchronous hatching in grebes provides a means by which parents can create initial asymmetries in the fighting potential of their newly hatched chicks, thereby promoting rapid formation of a self-regulating dominance system among their offspring.