INTERACTIONS AMONG ENVIRONMENTAL-STRESS, BODY CONDITION, NUTRITIONAL-STATUS, AND DOMINANCE IN GREAT TITS

We studied body condition and feather growth rate in Great Tits (Parus major) in relation to dominance in two localities during late autumn and early winter. The two localities differed in elevation, ambient te mperature, and arthropod availability. We supplemented the two study a reas with food (husked peanuts) throughout the study period. The perce ntage of time tits spent at feeders was higher at El Ventorrillo (the locality that was colder and had lower natural food availability) and was associated with dominance only at this locality. The number of agg ressive displacements per hour experienced by each individual was 150 times higher in the area with lower arthropod availability and lower t emperatures. Protein reserves (measured as pectoralis muscle thickness ) were higher at El Ventorrillo and were positively and consistently r elated to dominance at both localities. Growth rate of induced feather s was slower at Fl Ventorrillo but was not directly related to dominan ce in either locality. Only dominant adult males at El Ventorrillo com pensated for the environmental harshness at this locality by attaining a higher feather growth rate than the other sex/age classes. Feather- mass asymmetry of induced feathers during autumn was not associated wi th body condition, did not change between localities, and was inversel y and consistently related to dominance at both localities. The covari ation among variables describing bird size, access to supplemental foo d, body condition, feather growth rate, and asymmetry was different at the two localities. Larger, dominant Great Tits spent more time forag ing at feeders, had a thicker pectoralis muscle (i.e. body condition), and grew induced feathers at a higher rate only at the locality with colder temperatures and lower food availability.