Abstract
Theory predicts that individuals behave altruistically towards their relatives. Hence, some form of kin recognition is useful for individuals to optimize their behavior. In species that display bi-parental care and are subject to extra-pair matings, kin recognition theoretically can allow cuckolded fathers to reduce their parental investment, and thus optimize their fitness. Whether this is possible remains unclear in birds. This study investigates whether males provide differential parental care depending on relatedness, as a proxy to recognizing chicks in their nest as kin or not. We cross-fostered House sparrow (Passer domesticus) chicks after hatching, and then expected that fathers would show a decrease in their parental efforts when tending to a clutch of unrelated offspring. House sparrow males are able to adjust their parental care to the identity of their partner, making them an ideal study species. However, there was no significant effect of relatedness on provisioning rates. This suggests that sparrows may not be capable of kin recognition, or at least do not display kin discrimination despite its apparent evolutionary advantage.