Sample Behavior Review Paper
Extra-pair Copulation in Starlings (Sturnus vulgaris)
Extra-pair Copulations (EPC’s) are instances where an animal that has a mate copulates with an individual other than its mate. Starlings (Sturnus vulgaris) form pairs and both adults work together to raise their young. In a study of 14 starling families (including 62 chicks), DNA fingerprinting showed that 6 offspring were not the genetic offspring of the male at the nest. In one nest, there were chicks from three different males (Pinxten et al. 1993). In one case, the chick in the nest was not related to either of the adults tending the nest. This is called brood parasitism. It happens when a female lays an egg in another female’s nest. Before DNA fingerprinting was available, a lot of EPC’s were probably not detected. In the study described above, none of the EPC’s were actually observed by the researchers watching the birds.
In starlings, females usually solicit the within-pair copulations, but males were also observed soliciting the EPC’s (Pinxten and Eens 1996). The EPC solicitations happened when females were most fertile. Males also seemed to guard their mates more during this time, apparently to prevent EPC’s. If a male is off trying to copulate with a mated female, instead of guarding his own mate, is his own mate more likely to engage in EPC’s? In the study by Pinxten et al. (1993) there was no evidence of this.
Females might engage in EPC’s with males in order to get “better” genes, as evidenced by the fact that more dominant males, better ornamented males, and males with better territories get more EPC’s and have fewer non-related chicks in their own nests (Kempenaers et al. 1992).
Kampenaers, B., G. Verheyn, M. Van den Broeck, T. Burke, C. Van Broekhoven and A. Dhondt. 1992. Extra-pair paternity results from female preference for high-quality males in the blue tit. Nature 357:494-496.
Pinxten, R., O. Hanotte, M. Eens, R. Verheyn, A. Dhondt, T. Burke. 1993. Extra-pair paternity and intraspecific brood parasitism in the European starling, Sturnus vulgaris: evidence from DNA fingerprinting. Animal Behaviour, 45:795-809.
Pinxten, R. and M. Eens. 1997. Copulation and mate-guarding patterns in polygynous European starlings. Animal Behaviour, 54: 45-58.