Reduced levels of relatedness indicate that great-tailed grackles disperse further at the edge of their range

It is generally thought that behavioral flexibility, the ability to change behavior when circumstances change, plays an important role in the ability of a species to rapidly expand their geographic range. To expand into new areas, individuals might specifically show flexibility in dispersal behavior, their movement away from their parents to where they themselves reproduce. Great-tailed grackles ( Quiscalus mexicanus ) are a bird species that is rapidly expanding its geographic range and are behaviorally flexible. Here, we infer dispersal rates in wild-caught grackles from two populations across their range (an older population in the middle of the northern expansion front in Arizona nearer the core of their original range versus a young population on the northern edge of the expansion front in California) to investigate whether grackles show flexibility in their dispersal behavior between these two populations. Based on genetic relatedness, we observe no closely related pairs of individuals at the edge, suggesting that individuals of both sexes disperse further from their parents and siblings in this population than in the population nearer the core. Our analyses also suggest that, in both populations, females generally move shorter distances from where they hatched than males. These results elucidate that the rapid geographic range expansion of great-tailed grackles is associated with individuals, in particular females, differentially expressing dispersal behaviors.