The whistlers are stout birds with strong bills, and the group was once known as the thickheads due to the large rounded heads of many species. Their plumage is rufous, brown, or grey in the majority of species. Nevertheless, a few species, particularly the golden whistler and its close relatives, have bright plumage. One of the more unusual traits of this family is found in the feathers of some of the pitohuis, which have toxins. These toxins are probably a deterrent to parasites and may also serve to dissuade predators from taking the birds. Several species belonging to this family are outstanding songsters: the whistlers produce an astonishing volume for their size, and the lyrebirds aside, the grey shrikethrush is often regarded as the finest, most inventive songbird of them all.