Energy invested in reproduction by thick-billed murres ( Uria lomvia).

Abstract

Pelagic seabirds that lay single-egg clutches have been thought to invest less energy in reproduction than inshore-feeding species that rear >1 young. Time and energy budgets were calculated for thick-billed murres breeding at 2 large arctic colonies, and their energy expenditure compared with that of a hypothetical group (shirkers) capable of feeding at the same rate but not attempting any reproductive activity. The difference in energy investment between breeders and shirkers was strongly dependent on average foraging range. Results were also compared with similar estimates for inshore-feeding black guillemots Cepphus grylle. For the 2 thick-billed murre colonies, energy allocated to reproduction represented 30% and 24% of total energy expenditure during the breeding season, values exceeding estimates for black guillemots. -from Author