45.3 Saturday, Jan. 5 DYNAMICS OF FAT AND LEAN MASS IN REFUELLING MIGRANT PASSERINES MEASURED USING QUANTITATIVE MAGNETIC RESONANCE KENNEDY, L.V.*; GUGLIELMO, C.G.; University of Western Ontario email@example.com
Although fat deposition during stopover in migrating passerine birds has been extensively studied, changes in lean mass during refuelling are not well understood. I used quantitative magnetic resonance (QMR) analysis to measure the deposition of fat and lean mass for both recaptured and single capture migrant passerines in spring and fall at Long Point, Ontario. Both the recapture analysis and single capture regression analyses indicated a substantial contribution of lean mass to overall increases in total body mass across 18 species. Lean mass contribution to changes in total body mass is substantial, ranging anywhere from -35 to 113 % of mass increase and in some cases, was more dynamic than fat mass deposition during refuelling at stopover sites. The results of both regression and recapture analyses also suggest that smaller birds deposit relatively less lean mass and more fat per gram gained than larger birds. Our results support recent studies suggesting that lean mass is a dynamic body component during migration in all short-, medium- and long-distance migrant passerines. Thus, the accumulation of protein, and not just energy is an important driver in the foraging ecology of migratory birds.