Østnes, J.E. and C. Bech (1997). The early emergence of cold sensation in Shag nestlings Phalacrocorax aristotelis. J. Avian Biol. 28: 24-30.
Neonate Shags Phalacrocorax aristotelis do not respond metabolically to cold surroundings and depend completely for thermal protection on heat provided by the brooding parent. We examined whether neonate Shags have developed an ability to sense cold, even though a metabolic response to cold surroundings is completely absent. Such information is important in order to identify the sequence by which the different mechanisms needed to maintain a stable body temperature are developed. During cold exposure, 1-9 day old Shag nestlings were unable to produce heat by physiological means and responded to body cooling by vocalization. Nestlings 12 days old were able to maintain a stable body temperature during cold exposure and did not call. These results strongly suggest that neonate Shags have developed an ability to sense cold, which can trigger a behavioural thermoregulatory response well before they are capable of facultative thermogenesis. The lack of a metabolic cold response may be due to either the immature state of the skeletal muscles, or to an underdevelopement of neuromuscular connections. Vocalization is probably mediated by dynamic activity of thermoreceptors, as the body temperature per se seems to be of minor importance in terms of controlling the response. It is suggested that vocalization is mediated by fast-acting cutaneous thermoreceptors.