A Comparison of the Mitochondrial Performance between Migratory and Sedentary Mimid Thrushes.

This article investigates mitochondrial respiratory performance in the pectoralis muscle of two closely related bird species from the family Mimidae: the migratory Gray Catbird (Dumetella carolinensis) and the non-migratory Northern Mockingbird (Mimus polyglottos). Contrary to the hypothesis that migratory birds would exhibit higher mitochondrial respiratory capacity during migration, the study found no significant differences in mitochondrial respiration or electron transport system complex activities between the two species. However, Gray Catbirds showed a trend toward greater mitochondrial volume, and individuals identified as actively migrating displayed mitochondrial respiratory control ratios similar to those of Northern Mockingbirds, which are highly active year-round. The findings suggest that differences in daily activity patterns between species may confound comparisons of mitochondrial adaptations to migration, highlighting the importance of considering behavioral ecology when studying bioenergetic traits.