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the relationship between winter physiological condition and survival both within winter and among years.

Assuming that wintering birds increase their lean mass, fat reserves, metabolic performance and Het to improve their survival and that high condition reflects high individual ąuality, we expected positive relationships between physiological parameters and survival within winter as well as among years. However, according to the resource allocation principle (Weiner, 1992), birds facing challenging conditions, such as winter, could show physiological tradeoffs to support their main activities (i.e. thermogenesis and foraging) at the expense of other physiological Systems (e.g. immunity, self-maintenance) (Ardia & Clotfelter, 2007; Buehler et al., 2009; Wiersma et al._y 2004). Hence, the energy invested in developing and maintaining the winter phenotype could also potentially compromise winter survival {e.g. by a reduction of self maintenance) and result in long term negative cany-over effects on fitness (Fretwell, 1972; Saino et al., 2004). Conseąuently, we assumed the relationship between winter phenotype and survival to be non-linear, with maximal survival reached at an intermediate level of winter performance.

§.4 Materials and methods 5.4.1 Capture and handling

Our model species, the Black-capped chickadee, is a smali (9-14g), non-migratory, territorial, philopatric and short lived (3 years) passerine (Schubert et al., 2007; Schubert et al., 2008; Smith, 1991; Weise & Meyer, 1979), which makes it perfectly suited for this study. The study was carried out in the Foret d’Enseignement et de Recherche Macpfcs, Quebec, Canada (48° 18’ N, 68°31’ W) from October 2009 to December 2011. To facilitate capture and resighting, six feeding stations were set up during the first year and five stations were added during the second year, with an average distance between stations of 1.9 km. Each station included three metal feeders (Perky-Pet® 10" Sunflower Seed and Peanut Feeder) filled with black sunflower seeds. During captures (between 08:00 and 13:00), feeders were removed and homemade potter traps (15 cm x 15 cm x 15 cm) baited with seeds were used to catch birds. During the first winter (Sep 2009 to Mar 2010), we caught 139 birds (cohort 1), of which 72 were