Migratory body mass increase in Northern Wheatears [Oenanthe oenanthe) is the accumulation of fat as proven by quantitative magnetic résonance

摘要

Migratory birds need energy-rich fuel which is primarily gained through fattening. However, it is also hypothesised that birds store excess lean mass as an additional energy reserve during migration. Until now, changes in the fat of live birds could only be determined indirectly through the change in body mass and fat score. Recently, the full-body scanner EchoMRI~(TM) using quantitative magnetic résonance has become available making quick and précise measurements of whole-body compositions of livebirds (i.e., fat, lean and water mass) possible without sedating the birds. In this study, the EchoMRI~(TM) was applied on Northern Wheatears Oenanthe oenanthe hatched and reared in captivity during their first autumn migration stage. Results demonstrated that pre-migratory increase in body mass is primarily due to the fattening of the birds, while additional lean mass was not stored.