Thick-billed Grasswren (Eastern Subspecies) (Amytornis textilis modestus) (North, 1902) Recovery Plan

NSW National Parks and Wildlife Service, July 2002
ISBN 0 7313 65143

3 Distribution

3.1 Current and historical distribution

The Thick-billed Grasswren is endemic to inland Australia, with three isolated subspecies, all occurring in arid environments (Curry 1986; Ford 1987; Brooker 1988; Rowley & Russell 1997). The western subspecies, A. t. textilis, and the eastern subspecies, A. t. modestus, have undergone a substantial reduction in distribution since European settlement (Figure 1).

Figure 1. Current and former distribution of Thick-billed Grasswren (Amytornis textilis) in Australia
Figure 1. Current and former distribution of Thick-billed Grasswren (Amytornis textilis) in Australia (adapted from Rowley & Russell 1997 and Simpson & Day 1993). This map is indicative only.

In NSW, the Thick-billed Grasswren was collected on the lower Namoi River in 1847 (Gould), near Mossgiel in 1886 (Bennett) and south of Tibooburra in 1912 (MacGillivrey), indicating it had a widespread distribution in the state (Parker 1972; Morris et al. 1981; Ford 1987; McAllan 1987) (see Figure 2). A grasswren recorded in the Bulloorine in 1921 may have been this species, but it is thought more likely to have been a Grey Grasswren (Amytornis barbatus) (Chenery 1922; McAllan & Cooper 1995). The last documented record of a Thick-billed Grasswren in NSW was from a specimen acquired by the egg collector, Len Harvey, in 1956 near Tibooburra (McAllan 2000).

The Thick-billed Grasswren was once regarded as common around Mossgiel and Ivanhoe, but had 'almost entirely disappeared' by the 1880-90s (North 1901-14). Severe drought and land degradation caused by overstocking and Rabbit plagues around the turn of the century appear to be the main cause of the decline (Schodde 1982a; Ford 1987; McAllan 1987; Garnett 1993).

Figure 2. Records of the Thick-billed Grasswren (Amytornis textilis ssp. modestus) in NSW
Figure 2. Records of the Thick-billed Grasswren (Amytornis textilis ssp. modestus) in NSW (NSW NPWS Wildlife Atlas). This map is intended to be indicative only.

Given the lack of records of the species in NSW over the last half century, it could be suggested that the Thick-billed Grasswren is already extinct in this state. However, no targeted surveys have been undertaken in NSW in recent times. Accordingly, there remains conjecture as to its status in NSW (Morris et al. 1981; Blakers et al. 1984; McAllan 1987; Cooper & McAllan 1995, McAllan 2000) and it is still possible that the species remains extant within NSW.

3.2 Movements

The Thick-billed Grasswren is sedentary or resident (Schodde 1982a; Brooker 1988; Gee et al. 1996; Rowley & Russell 1997) and has been recorded in all seasons (Hall 1910; Morgan 1923; Sutton 1923, 1927; Cox 1974; Badman 1979; Joseph & Black 1983; Matthew & Carpenter 1993; Coate 1994; SA Bird Repts). Pairs may remain in the same 4-5 ha throughout the year, whereas other grasswrens tend to congregate into locally nomadic parties after breeding (Schodde 1982a). Sedentary birds may during particularly dry periods undertake some nomadic movements (Serventy et al. 1982).