A field study of temperature regulation in young white pelicans, Pelecanus erythrorhynchos
Bartholomew, G.A.; Dawson, W.R.; O'neill, E.J.
Ecology 34(3): 554-560
ISSN/ISBN: 0012-9658 DOI: 10.2307/1929727
Both naked and downy young white pelicans have diurnal temp. cycles with mean night body temps. more than 4[degree]C lower than mean day temps. Overheating is primary temp. problem faced by young pelicans in unshaded rookeries in Salton Sea in desert region of so. California. During heat of day, adults shade eggs and naked young, but older, downy young remain exposed to intense solar radiation. At this time downy young form loose groups in shallow water near shore. Mean body temp. of swimming young was 38.5[degree]C and that of dry young of similar size exposed to sun was 41.9[degree]C. Both downy young and adults flutter their large gular pouches almost continuously during hot weather. Survival of young when exposed to high air temps. and direct solar radiation depends upon behavioral patterns tending to reduce heat stress, use of the gular pouch for evaporative cooling and ability to tolerate elevations of body temp. to as much as 43[degree]C.