The adult male, which weighs 29.8-32.5 g, possesses a rufous coloured chin and throat from its third year of life, as does its most likely closest relative, the red-lored whistler. Both males can easily be differentiated by the colour of their lores: black for the Gilbert's and red for the red-lored whistler. The female Gilbert's whistler (23.5-32.2 g) has a pale grey throat and a white ring around the eye; her underparts can be lightly streaked. Both sexes are uniformly brownish-grey, and have a red iris and a black stubby bill (17–18 mm). Juveniles (30.9 g) are darker than adults, with tinges of brown, and have dark streaks on the breast and belly. Immatures are very similar to adult females except for their brown bill and dark brown iris. Care should be taken not to mistake the female and immature Gilbert's whistler for the female golden or western whistlers where they co-exist.
At one stage, the Gilbert's whistler was divided into two subspecies: Pachycephala inornata inornata in the east of the Flinders Ranges with greyish white underparts, and Pachycephala inornata gilberti in the west with cinnamon and buff underparts; this variation is now considered clinal.
A study undertaken by Onley, Gardner and Symonds (2020) on possible larger appendages in whistlers caused by climate change (Allen's rule) from museum specimens collected between 1915 and 2013, found an increase in the body size of the Gilbert's whistler at higher latitudes, following Bergmann's rule.
Gilbert's whistlers feed mostly on the ground, as does about half of all declining species of birds in southern Australia. This species also forages in understorey layers. They feed primarily on invertebrates, although fruit and seeds can also form part of its diet.
Of the four states in which the Gilbert's whistler occurs, this species is listed vulnerable only in New South Wales under the NSW Biodiversity Conservation Act 2016 based on population decrease in size and distribution. A conservation strategy was developed in 2015 as part of the Saving our Species program with some of the priority management areas including: restoring native vegetation, removing weeds, implementing actions to reduce the impact of noisy miners when deemed necessary, encouraging landholders to implement sensitive grazing practices, strip burning with refuge areas remaining unburnt for 25 years or more, raising public awareness of the importance of large old trees, revegetating, and identifying methods to improve soil quality.
The Gilbert's whistler is not listed at national level under the Environment Protection and Biodiversity Conservation Act 1999, and is listed as least concern at international level under the IUCN Red List of Threatened Species 2016.
