HEAT INCREMENT OF FEEDING IN BRUNNICH GUILLEMOT URIA-LOMVIA

The rate of oxygen consumption ((V) over dot(O2)), respiratory quotien t (RQ) and deep body temperature (TB) were recorded during a single, v oluntary ingestion of Arctic cod Boreogadus saida (mean mass 18.9+/-1. 1 g, S.E.M., N=13) by five postabsorptive Brunnich's guillemots (thick -billed murre, Uria lomvia). The birds were resting in air within thei r thermoneutral zone, and the fish were refrigerated to 0-2 degrees C, The rate of oxygen consumption increased by a factor of 1.4 during th e first few minutes after ingestion, but there was no significant chan ge in T-B. Mean rate of oxygen consumption returned to preingestive le vels 85 min after the birds ate the fish, The telemetered temperature of one fish reached T-B within 20 min, This suggests that the persiste nt elevation in (V) over dot(O2) over the next hour corresponded to th e obligatory component of the heat increment of feeding (HIF) and was not related to heating the fish, Abdominal temperature increases after diving bouts in free-ranging common guillemots (common murre, Uria aa lge) are possibly achieved through the HIF, since meals are processed at sea, Of the increase in (V) over dot(O2), measured in the laborator y, it is calculated that 30 % is required to heat the fish, while 70 % is due to the HIF. In free-ranging birds, the excess heat provided by the HIF could contribute 6 LTC of the daily energy expenditure, This suggests that the HIF augments heat production in Uria spp. and thus r educes the energetic cost of thermoregulation.