Additional files [RJEE Vol. 5 (3). 2020 – 5]

• Fig. 1. Model bird species used in population studies (see text for details), the European pied flycatcher Ficedula hypoleuca (left) and the great tit Parus major (right)
• Fig. 2. A principal scheme of how an increase in basal metabolic rate (BMR) can affect the morphological and physiological properties (and ultimately the social rank) of individuals and how the rank is correlated with morphological and population properties. Arrows show links that are common to all animals; bold lines in the lower part of the diagram show statistically significant correlations established for the great tit; dashed lines indicate statistically insignificant relationships. Tb is body temperature