Territory quality drives intraspecific patterns of extrapair paternity

Abstract

Despite the potential reproductive benefits of extrapair matings, extrapair paternity rates in many avian species often vary greatly among populations. Although ecological factors have been shown to influence intraspecific patterns of extrapair paternity in some species, for cooperatively breeding species living in family groups, social/demographic factors may also play a role. This study examined how ecological factors related to territory quality (vegetation cover, insect abundance) and social/demographic factors (group size, number of breeding pairs, genetic relatedness) influenced intraspecific patterns of extrapair paternity in cooperatively breeding superb starlings, Lamprotornis superbus. Superb starlings inhabit spatiotemporally variable African savannas where high temporal variability drives reproductive decisions (adoption of breeding roles, offspring sex allocation) and where territories suitable for breeding are limited. Although extrapair paternity rates were only 14% of offspring and 25% of nests, they varied greatly among groups, ranging from 4% to 32% of offspring and from 7% to 60% of nests. These among-group differences in extrapair paternity were not related to social/demographic factors but instead to territory quality; extrapair paternity was higher on lower quality territories (lower vegetation cover and grasshopper abundance) than on higher quality territories (higher vegetation cover and grasshopper abundance). These results suggest that even in a heterogeneous landscape where suitable breeding territories are limited, subtle differences in habitat quality can have profound effects on reproductive decisions and patterns of extrapair paternity. Understanding the interaction between spatial (habitat heterogeneity) and temporal (temporal variability) environmental variation will be important for determining how environmental and social factors drive avian reproductive and mating decisions. © The Author 2007. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.