How a hybrid zone is maintained: behavioral mechanisms of interbreeding between California and Gambel's quail (Callipepla californica and C. gambelii).

Hybridizing California and Gambel's Quail (Callipepla californica and C. gambelii) are unlike many hybridizing avian species in that pairing primarily occurs within a flock, or covey, that is composed of several families. Coveys in the area of sympatry contain mostly hybrid individuals, relative to parental types. I tested whether individuals perceive covey mates as a single species and whether pairing within the covey causes inbreeding and a loss of reproductive success. Individuals discriminated between the parental species in captivity, but actual pairing in the wild was random with respect to species. Contrary to expectation, coveys were not more inbred than the local population. Results suggest that potential costs of inbreeding may be avoided through sex-biased dispersal and nonrandom pairing. Furthermore, breeding occurred earlier and with greater success in pairs formed within the resident covey, rather than outside it. These findings suggest that fitness benefits gained from pairing early within a mixed-species covey promote interspecific pairing. This study provides evidence that mating behaviors specific to local conditions maintain hybrid zones when genetic costs to interbreeding are small.