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& Li, 2006; Maldonado et al., 2009; Zheng et al., 2008), while Msum would be mainly influenced by exercise organs such as breast muscles and heart (Chappell et al._y 1999; Cooper, 2002; Liknes & Swanson, 201 lb; 0'Connor, 1995).

4.4 Materials and methods 4.4.1 Capture and handling

We captured 79 free-living Black-capped chickadees (42 males and 37 females) within the Foret d’Enseignement et de Recherche Macpes, Quebec, Canada (48° 18’ N, 68°31’ W) from November 12* to 22^nd 2010 (fali, mean temperaturę on site: -0.7 ± 5.2°C, n = 20), February 3"¹ to 15* 2011 (midwinter, mean temperaturę on site: -11.9 ± 5.1 °C, n = 28), March 23^rd to 3l^sl 2011 (end of winter, mean temperaturę on site: -3.9 ± 4.3°C, n = 20) and August 11* to 21^st 2011 (summer, mean temperaturę on site: non available, mean temperaturę recorded by the closest weather station 19 km away: 19.1 ± 1.9°C, n = 11). To attract chickadees and facilitate capture, 16 feeding stations were set up with an average distance between stations of 1.9 km (Lewden et al_t 2012; Mandin & Vezina, 2012). Feeders were regularly filled with black oil sunflower seeds. On capture days, feeders were removed and homemade potter traps (15 cm x 15 cm x 15 cm) baited with black oil sunflower seeds were used. Ali birds were caught between 08:00 and 13:00 and handled in less than ten minutes following capture.

We weighed birds and measured the lengths of their beak, head plus beak, tarsus, taił and wing (Pyle, 1997). Following these measurements and depending on capture success, up to four birds per day were brought to the field station for metabolic measurements. Ali bird manipulations were approved by the animal care committee of the Universitć du Qućbec & Rimouski and have been conducted under scientific and banding permits from Environment Canada - Canadian Wildlife Service.

4.4.2 Respirometry

Ónce at the field station, birds were maintained in separate cages (39 cm x 43 cm x 31 cm) supplied with food (sunflower seeds) and water ad libitum until measurements. Cages were