... is poorly understood. We investigated flexibility in traits that affect thermal balance between black-capped chickadees ( Poecile atricapillus ) acclimated for 6 weeks to cold (−5°C) or control (23°C) environments ( n =7 per treatment). We made repeated measurements of basal and summit metabolic rates via...

... hyemalis ) to chronic cold acclimations of varying duration and subsequently quantified their metabolic rates, thermal conductance and ability to maintain normothermia. Cold-acclimated birds adjusted traits related to both heat generation (increased summit metabolic rate) and heat conservation (decreased...

...Magali Petit; François Vézina In small resident bird species living at northern latitudes, winter cold acclimatization is associated with an increase in pectoral muscle size and haematocrit level, and this is thought to drive the seasonal increase in summit metabolic rate ( Ṁ sum , a measure...

.... Competing interests The authors declare no competing financial interests. 3 9 2013 10 11 2013 © 2014. Published by The Company of Biologists Ltd 2014 Phenotypic flexibility Summit metabolic rate Photoperiod Temperature Dark-eyed juncos Birds Pectoralis Citrate synthase β...

... of physiological adjustments, ranging from biochemical transformations to organ mass variations, are involved in this process. Several studies have shown that improved cold endurance is accompanied by increases in summit metabolic rate( M sum ), a measure of maximal heat production and an indicator of the level...