Taxonomic significance of some hybrid and aberrant-plumaged quail-thrushes

Abstract

New data are given on the distributions of the Chestnut-breasted Quail-thrush Cinclosoma castaneothorax and the Cinnamon Quail-thrush C. cinnamoneum in Queensland. Hybridization in western Queensland is reported and interpreted; the two taxa are considered conspecific. An apparently hybrid female between C. cinnamoneum marginatum and C. castonotum clarum from the Great Victoria Desert is described; extensive sympatry between these two forms shows that the hybrid does not indicate conspecificity but merely close relationship. An unusually plumaged male Cinclosoma from the Northern Territory, similar in coloration to the Nullarbor Quail-thrush C. alisteri, may be an aberrant C. castonotum clarum or a hybrid clarum x marginatum: if an aberrant clarum, castonotum and alisteri are probably more closely related to each other than to any other species of the genus, but if a hybrid, the disposition of black on the undersurface of males is probably not a reliable guide to relationships in the genus. Ecological isolation of C. castonotum from C. alisteri where their ranges abut indicates that they are not conspecific. The relationship between C. cinnamoneum and C. alisteri is discussed but data are insufficient to assess whether they are conspecific. An aberrant-plumaged female of C. cinnamoneum castaneothorax from Moombidary, Q, is re-examined and considered to have no special characters that indicate close relationship with C. castonotum and the New Guinea Quail-thrush C. ajax. Some previous records of C. castonotum clarum are assessed; no observations of this taxon from the Lake Eyre region are accepted.