There is a lot of variation in the Brown Thornbill complex (includes Inland Thornbill). Although the pictures below show quite a difference between the Brown and Inland, such is not always the case. There are extensive zones of overlap of these two species in which some individuals can be hard to identify. It is a very complex situation and dealt with fully in "The Directory of Australian Birds" by Schodde & Mason. Probably the most unusual thornbill in this group is the very pale form once known as the Whitlock Thornbill in Cayley's "What Bird is That?" It can be seen in the paperbark swamps along the northern highway on Anna Plains Station between Port Hedland and Broome in W.A. Another problem in identification in this dark-eyed group can arise in separating Inland from Slaty-backed Thornbills. Both species live side by side in the mulga zones of arid Australia. Juvenile Inland Thornbills from parts of Queensland (and probably elsewhere) can have little or no markings on the breast or forehead - very plain birds indeed! The streaked (NOT scalloped) crown of the Slaty-backed (see xxx003) is not always easy to see as they forage in the foliage of the mulgas, but it is the only really reliable field mark. Unfortunately, juvenile Slaty-backs are also very plain birds indeed, lacking all distinctive markings and it would take a real expert to distinguish these two juveniles in the field.