SUMMARYFORD, J. 1986. Avian hybridization and allopatry in the region of the Einasleigh Uplands and Burdekin-Lynd Divide, north-eastern Queensland. Emu 86; 87–110.The Einasleigh Uplands and Burdekin-Lynd Divide comprise an elevated section of the Great Dividing Range in northeastern Queensland. About twenty avian species of eucalypt forest, woodland and grassland habitats have range gaps, hybrid zones or stepped size-clines in the region of these uplands. Species and species-pairs with a discontinuous or partly discontinuous range include the Lemon-bellied FlycatcherMicroeca flavigaster, Restless FlycatcherMyiagra inquieta, White-gaped HoneyeaterLichenostomus unicolor, Yellow HoneyeaterLichenostomus flavus, Fuscous/Yellow-tinted HoneyeatersLichenostomus fuscus/flavescens, Bar-breasted HoneyeaterRamsayornis fasciatus, Crimson FinchNeochmia phaeton, Star FinchNeochmia ruficaudaand Chestnut-breasted MannikinLonchura castaneothorax.Those with a hybrid zone are the Squatter PigeonPetrophassa (Geophaps) scripta, Pale-headed RosellaPlatycercus adscitus, Brown TreecreeperClimacteris picumnus, Black-chinned HoneyeaterMelithreptus gularis, Striated PardalotePardalotus striatusand Black-throated FinchPoephila cincta.Stepped size-clines or sharp morphological changes occur in the Brown GoshawkAccipiter fasciatus, Barking OwlNinox connivens, Masked OwlTyto novaehollandiae, Tawny FrogmouthPodargus strigoidesand Laughing KookaburraDacelo gigas.Though some of the hybrid zones and steps might have been produced by nearby geographical barriers consisting of low rainfall salients, the upland-divide is an active barrier at present. A cooler climate in the upland-divide now, and presumably in past times, appears to be the cause of present and past range gaps because relevant habitats are continuous throughout north-eastern Queensland. Two taxa,Accipiter fasciatusandMelithreptus gularis, might each be composed of two species; because the small (didimus) and large (fasciatus) forms ofA. fasciatuspossibly both occur in tropical Australia throughout the year rather than only in winter when the large form is presumed to be a southern migrant; and the evidence for hybridization between the altitudinal vicariant formsgularisandlaetioris equivocal. Most geographical barriers between isolated avian populations on the Australian mainland to consist of arid or low-rainfall belts extending to the coast but other cold upland sections of the Great Dividing Range besides the Einasleigh Uplands and Burdekin- Lynd have operated as barriers. These include the McPherson Range and Blue Mountains—Snowy Mountains chain.