title: How does flexibility in body composition relate to seasonal changes in metabolic performance in a small passerine wintering at northern latitude?
abstract: Abstract Small avian species wintering at northern latitudes typically show increases in basal metabolic rate (BMR) and maximal thermogenic capacity (Msum). Those are widely assumed to reflect changes in body composition, with enlargement of digestive and excretory organs resulting in elevated winter BMR and larger body muscles driving the increase in Msum. Using free-living black-capped chickadees (Poecile atricapillus) as our model species, we investigated seasonal changes in body composition and tested for relationships between mass variations of body organs and variability of both BMR and Msum. Our results confirmed the expected winter increase in mass of body muscles and cardiopulmonary organs (heart + lungs) and showed that 64% of the observed Msum variations throughout the year were explained by changes in these organs. In contrast, we found little support for an effect of the digestive organs (gizzard + intestines) on BMR seasonal changes. Instead, this variable was mainly influenced by variations in mass of body muscles and excretory organs (liver + kidney), explaining up to 35% of its variability.
authors.affiliation: Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada; 2Centre de la Science de la Biodiversité du Québec, Montréal, Québec H3A 1B1, Canada.
authors.forename: Magali
authors.initials: M
authors.lastname: Petit
authors.forename: Agnès
authors.initials: A
authors.lastname: Lewden
authors.forename: François
authors.initials: F
authors.lastname: Vézina
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D001481:Basal Metabolism / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D004777:Environment; D046109:Passeriformes / Q000502:physiology*; D012621:Seasons; D022722:Thermogenesis