Thick-billed Grasswren (Eastern Subspecies) (Amytornis textilis modestus) (North, 1902) Recovery Plan
NSW National Parks and Wildlife Service, July 2002
ISBN 0 7313 65143
Other Common Names:
|Amytornis textilis modestus (North, 1902)
Thick-billed Grasswren (eastern subspecies)
A. modestus, Diaphorillas modestus
The Thick-billed Grasswren is a passerine of the family Maluridae (Christidis & Boles 1994). Grasswrens are the largest genus in the family Maluridae, with ten species currently recognised (Rowley & Russell 1997; Christidis 1999, Higgins et al. 2001). Species in the genus are distributed across much of arid and tropical Australia.
The Thick-billed Grasswren is polytypic with three subspecies currently recognised: a western subspecies, A. t. textilis, an eastern subspecies, A. t. modestus, and a subspecies occurring in the Gawler Ranges of SA, A. t. myall (Schodde 1982a; Rowley & Russell 1997). Only A. t. modestus is found in western NSW. This subspecies is also found in north-eastern SA and southern NT.
Grasswrens are a cryptic species, well camouflaged for survival in the sparsely vegetated habitats in which they are so often difficult to locate. Grasswrens are similar in appearance to Fairywrens being small with long cocked tails. Their wings are short and rounded. Flight, although rare, is similar to other Malurids with the tail drooped downward. Grasswrens spend most of their time on the ground, running and hopping in search of seeds and insects (Rowley & Russell 1997). The genus occupies remote areas of spinifex, mallee, lignum, canegrass and saltbush.
The Thick-billed Grasswren has a short thick bill and is paler overall than the other thin-billed species. It is grey-brown above with a darker crown and fawn brown below, dully marked over head, back, throat and breast with off-white streaks (Rowley & Russell 1997; Schodde & Mason 2001). The sexes differ slightly in plumage, with the female having chestnut flanks. The other subspecies are more boldly streaked and have a longer tail that is sexually disproportionate (McDonald 1988; Schodde & Mason 2001). Adult birds have a total length of 15-20 cm, wings length is 59-63 mm and tail length is 70-80 mm (Rowley & Russell 1997; Schodde & Mason 2001). Adult birds weigh 19-24 g (Rowley & Russell 1997).
Thick-billed Grasswrens are thought to vocalize less frequently than any other grasswren (Carter 1917; Whitlock 1924; Rowley & Russell 1997). Morcombe (2000) described the calls of A. t. modestus as an extremely high, soft 'see-see-see' and a brief squeaky trill 'see-see, tsewit-tsewit'. Schodde (1982a) describes several calls including a clear silvery song; a low pitched chirping 'teck-teck'; and high pitched alarm squeaks. Males sometimes break into short, reedy, metallic whistles from vantage perches during the peak of the breeding season (Schodde 1982a).