Is mass loss in Brünnich’s guillemots Uria lomvia an adaptation for improved flight performance or improved dive performance?

• Main Authors: Kyle H. Elliott, Shoshanah R. Jacobs, Julian Ringrose, Anthony J. Gaston, Gail K. Davoren, K. H. Elliott (correspondence, G. K. Davoren
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2008
• Subjects: Coats Island; Nunavut; Uria lomvia; uria
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.579.1966; http://play.psych.mun.ca/~mont/pdfs/brunnichs.PDF

Breeding Brünnich’s guillemots Uria lomvia show stepwise mass loss at the time of hatch. This mass loss has usually been explained as an adaptation to reduce the cost of flight during the chick-rearing period because flight time increases during that period. It is possible, however, that mass loss also increases dive performance during the chick-rearing period because time spent diving also increases during that period. Reduced mass could reduce basal metabolic rate or costs associated with buoyancy and therefore increase aerobic dive limit. To examine the role of mass loss in dive behavior, we attached time-depth-temperature recorders for 2448 h to chick-rearing and incubating Brünnich’s guillemots at Coats Island, Nunavut (2005: n45, 2006: n40), and recorded body mass before and after each deployment. There was no relationship between mass and dive duration during either incubation or chick-rearing. Seventeen of the birds we sampled during incubation were resampled during chick-rearing. For this group, dive duration increased with mass loss between incubation and chick-rearing (r20.670.75). Mass loss occurred through reductions in metabolically-active tissues (liver, bladder) and buoyant tissues (lipids) although muscle and gut mass did not change. Despite the large change in lipids, buoyancy only changed by 0.1%, and mass loss therefore did not have much effect on costs associated with buoyancy. Nonetheless, surface pause duration for a given dive depth decreased during chick-rearing, supporting the idea that reduced mass led to increased aerobic dive limit through reduced metabolic rate and inertial costs; oxygen stores did