Feeding frequencies and nest defence of Fieldfares in relation to body size, physical condition and sex of parents

Abstract

Nestling care is an energetic demanding period for most parents of altricial birds, and the parents relative contribution to nestling feeding rates may differ. The mean feeding rate of one-week old nestlings (number of nest visits per hour) by Fieldfare females was lower than that of males. The sexes did not differ in physical condition (based upon the amount of subcutaneous fat visible in the furculum or body-mass:wing-length ratio) in the nest building and egg-laying periods, but after hatching the females had decreased in body mass and physical condition whereas males did not. Males, but not females, increased their intensity of nest defence after hatching. Large males (based on wing length) had a higher feeding rate than smaller ones, whereas large females had not.