For my doctoral research, I investigated sex differences in breeding dispersal decisions of a socially monogamous, territorial songbird, the prothonotary warbler (Protonotaria citrea). I used experiments to influence dispersal decisions based on public information, that is, conspecific reproductive success, and private information pertaining to the genetic mating system. Unsuccessful individuals are the most dispersive and therefore became the primary focus of my research. Males and females both appeared to use public information in their dispersal decisions. Males returned between years to good neighborhoods whereas females returned to good patches.

What appeared to be public information, in fact, was mostly private information. Unsuccessful male warblers based their between-year neighborhood fidelity on either the fledging of extra-pair (EP) offspring, or if unsuccessful on all fronts (i.e., own nest and EP mating), neighborhood quality. Unsuccessful females, in contrast, returned between years to their patch if they had cuckolded their mate, but moved farther based on the relatedness to their social mate. Females were more likely to cuckold their social mate the more closely they were related.

Further experimental examination of male dispersal decisions revealed that males were aware of their fledged EP offspring. Either through kin-recognition or copulating with known females that subsequently fledged their broods, males were able to discern between fledged and failed nests containing their EP offspring.

In order for dispersal decision rules to evolve, the factor affecting their dispersal must be predictable between years. Males that returned to a familiar site were more likely to gain EPFs than those males immigrating into an unfamiliar site. Age, which is often correlated with experience and EP mating success, was no longer important in predicting EPFs after controlling for experience. Experienced males were cuckolded at similar rates to inexperienced males which suggested that quality was not influencing the effect of experience on EPFs. Males returned to areas with more EP mating opportunity and produced more offspring, which is not possible for females in this system. Hence, cuckoldry or EP mating has directly opposite effects on male and female dispersal decisions and conforms nicely to Greenwood’s prediction that the prevailing mating system can explain patterns of sex-biased dispersal.