Journal of the Royal Society of Western Australia, 86(4), December 2003 
patterns we observed provide a strong indication as to 
which habitats act as drought refugia. 
Methods 
Bird censuses were carried out from 30 ,h August to 4 th 
September 1994 between 0730 and 1700 at 21 sites in 
Wanjarri Nature Reserve. Birds were assessed by the 
square transect method (Biological Survey Committee 
1984). At most sites we set up two 200 x 200 m square 
grids. Both authors walked the four sides and one 
diagonal of one square at each site, over approximately 
45 minutes, and recorded all birds seen or heard within 
30 m of either side of the transect line. On those sites 
where the habitat features were linear (such as creeklines 
and breakaways), we conducted counts on two linear 
1080 m transects rather than 200 x 200 m squares. At all 
sites, we added the results from the two censuses. Birds 
seen or heard outside the 60 meter transect band, or only 
seen flying overhead, were recorded as opportunistic 
records. The time at which censuses were conducted in 
different habitats was randomised with respect to time of 
day to reduce any bias from variations in bird activity 
through the day. The counts in 1994 were conducted in 
what we considered drought conditions, because only 
87.4 mm of rain had fallen in the 12 months prior to 
September 1994 at Albion Downs, 30 km N of Wanjarri 
(Fig 1). This compares with the average annual rainfall at 
Albion Downs of 237.8 mm. 
Habitats 
The 21 sites censused for birds were divided into four 
broad habitat types; (1) groving and creekline mulga 
communities (5 sites), (2) open mulga communities (5 
sites), (3) spinifex communities (4 sites), and (4) other 
communities (7 sites). The four community types were 
defined as follows; 
(1) groving and creekline mulga communities: those 
where mulga ( Acacia aneura) grew to 10 m in either major 
shallow drainages, which were up to 350 m wide, or 
where mulga occurred in discrete groves independent of 
any co-ordinated drainage. In landscape terms, the 
drainages formed corridors of denser vegetation between 
the granite-dominated high points and the lower spinifex 
plains. Foliage cover was usually around 25-30%. A wide 
variety of shrubs and grasses were often present, 
including Grevillea sarissa, Rhagodia eremaea, Solatium 
lasiophyllum and Gtiephosis foliata , and dense leaf litter, 
sometimes redistributed by flooding, was usually a 
feature of this community type. 
(2) open mulga communities: those where mulga was 
the structurally dominant plant as either a small tree or a 
shrub. Foliage cover was around 15-20%. A wide variety 
of lower shrubs or grasses were often present, including 
Acacia ligulata, Eremophila fraseri, Eragrostis eriopoda and 
Aristida contorta . When Triodia basdowii was present, it 
was relatively uncommon and did not achieve the large 
clump size that it did on sandier soils. 
(3) spinifex communities: those in which Triodia 
basdoiuii was the dominant plant species and formed a 
foliage cover of 30-70%. Spinifex communities occurred 
either on open plains or as a dune/swale sequence. 
When they occurred on open plains, the overstorey was 
dominated by either mallees (Eucalyptus oldfieldii and £. 
leptopoda) or wattles (Acacia aneura, A . pachyacra and A. 
coolgardiensis) depending on soil characteristics. When 
they occurred as a dune/swale sequence, then £. 
gongylocarpa, Grevillea pterosperma and A. ligulata were the 
100 
Figure 1. Monthly rainfall data for Albion Downs station about 30 km N of Wanjarri from January 1992 until September 1994. Note that 
the six months prior to the September 1994 survey were very dry although February 1994 had been relatively wet. 
134 
