Non-breeder asymmetry in Florida Scrub Jays

Summary The data of Woolfenden and Fitzpatrick (1984) show a statistically significant asymmetry in the sex ratio of non-breeders when one of the breeders is not the non-breeder's parent. I propose that the asymmetry is attributable to a combination of two factors acting on non-breeders: the value of inheriting a territory, and incest avoidance. Although natal territories are only occasionally inherited by non-breeders, and then apparently only by males, therate of inheritance is significantly higher for parent/step-parent breeders (n=6) than when both breeders are the non-breeder's parents (n=1). An alternative hypothesis, that stepparents determine the non-breeder asymmetry by ousting potential rivals, might also explain the data, but evidence is currently lacking.