Da. Croll et E. Mclaren, DIVING METABOLISM AND THERMOREGULATION IN COMMON AND THICK-BILLED MURRES, Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology, 163(2), 1993, pp. 160-166
The diving and thermoregulatory metabolic rates of two species of divi
ng seabird, common (Uria aalge) and thick-billed murres (U. lomvia), w
ere studied in the laboratory. Post-absorptive resting metabolic rates
were similar in both species, averaging 7.8 W.kg-1, and were not diff
erent in air or water (15-20-degrees-C). These values were 1.5-2 times
higher than values predicted from published allometric equations. Fee
ding led to increases of 36 and 49%, diving caused increases of 82 and
140%, and preening led to increases of 107 and 196% above measured re
sting metabolic rates in common and thick-billed murres, respectively.
Metabolic rates of both species increased linearly with decreasing wa
ter temperature; lower critical temperature was 15-degrees-C in common
murres and 16-degrees-C in thick-billed murres. Conductance (assuming
a constant body temperature) did not change with decreasing temperatu
re, and was calculated at 3.59 W.M-2.-degrees-C-1 and 4.68 W-M-2.-degr
ees-C-1 in common and thick-billed murres, respectively. Murres spend
a considerable amount of time in cold water which poses a significant
thermal challenge to these relatively small seabirds. If thermal condu
ctance does not change with decreasing water temperature, murres most
likely rely upon increasing metabolism to maintain body temperature. T
he birds probably employ activities such as preening, diving, or food-
induced thermogenesis to meet this challenge.