Colour morph does not predict brood size in the Booted Eagle

Abstract

Mechanisms regulating colour polymorphism remain largely unknown and detailed investigation is required to explore the biological consequences on population dynamics. This paper presents the first study of the possible connection between colour polymorphism and productivity in aBooted Eagle (Aquila pennata) population breeding in southeastern Spain. To that end we used 19 years of data of non-marked individuals. Atotal of 738 pale (91.6%) and 68 dark (8.4%) adult Booted Eagles were observed in our study area, including 57 territories. Our results suggest that colour morph of both sexes remained stable in the population over the study period. Although we found a higher number of offspring produced by parents exhibiting the dark morph than those of the pale morph, statistical differences were not significant. Hence, ourmodels showed that colour polymorphism was not a good predictor of Booted Eagles’productivity, although further research by capture-recapture analysis would be needed to explore the influence of colour variation on fitness components at individual level and its consequences at population level of long-lived species.