Body size, body condition and ornamental feathers of Burrowing Parrots: variation between years and sexes, assortative mating and influences on breeding success

Abstract

Individual size and body condition determine the breeding success in many species of birds. We here present morphometric data and describe the relationships between body size, body condition, breeding success and ornaments of genetically sexed Burrowing Parrots (Cyanoliseus patagonus), including data from a year of adverse environmental conditions caused by the strong La Niña phase of the El Niño Southern Oscillation phenomenon of 1998–99. During droughts caused by La Niña, adults invested more resources in their own body maintenance and decreased provisioning to nestlings, as shown by higher adult body masses and body conditions, and increased nestling mortality due to starvation. We found slight sexual dimorphism, male Burrowing Parrots being structurally larger (~5%) than females. Adult Burrowing Parrots mated assortatively with respect to body condition and the size of the red feather patch in the centre of the abdominal region. We identified the red abdominal patch as a signal of individual quality. We also present correlations of adult body mass, body condition, measurements of structural size and ornaments, with parameters of breeding success and nestling growth. Female Burrowing Parrots in better body condition fledged heavier nestlings. Parameters of structural size of male Burrowing Parrots correlated with structural characters of the nestlings such as bill and tarsus length, and wing growth.