Pruett-Jones & O'Donnell: Land Birds on Barrow Island 
Table 2 
Number of individuals of each species recorded on quadrats and total population estimates for Barrow Island in comparison with the 
estimates of Sedgwick (1978). 
Species 
Quadrat 
counts 
Total population 
estimate based on 
this study 
Population estimate 
from Sedgwick 
(1978) 
Spotted Harrier 
3 
162 
180 
Brahminy Kite 
2 
23 
15 
Osprey 
1 
73 
180 
White-breasted Sea-Eagle 
1 
73 
3 
Australian Kestrel 
1 
69 
1,650 
Bar-shouldered Dove 
14 
692 
180 
Black-eared Cuckoo 
2 
67 
No estimate 
Horsfield's Bronze-Cuckoo 
5 
102 
910 
Sacred Kingfisher 
1 
6 
12 
Welcome Swallow 
36 
1,077 
8,500 
Tree Martin 
1 
6 
7,050 
Spinifexbird 
404 
24,623 
17,800 
White-winged Fairy-wren 
132 
7,519 
8,150 
Singing Honeyeater 
101 
3,920 
3,050 
Zebra Finch 
32 
1,152 
No estimate 
White-breasted Woodswallow 
41 
1,945 
3,450 
to maximum vegetation height (F x 29 = 10.913, P = 0.025) 
and to the mean emergent score (F t 29 = 5.860, P = 0.022). 
We combined data from each of the six major habitat 
zones to examine broad scale habitat relationships within 
the avifauna. We compared species number, total number 
of individuals, and mean bird density across these six 
habitat zones according to each of the habitat variables. 
The number of species recorded in each habitat was 
significantly correlated with maximum vegetation height 
(Spearman Rank Correlation R s = 0.929, P = 0.038) but no 
other significant correlations were observed. 
Effects of Oil-field Development 
Our study of the effects of the oil-field development 
was limited to four vegetation zones as described in 
Methods: three limestone ridge habitats (LI, L3, and L7) 
and one valley habitat (VI). 
We first examined whether within each of these 
habitat types, the vegetation differed between natural 
areas, around oil-pads, and along roadsides. Within 
habitat LI, there was significant variation in vegetation 
cover between these areas (P 2 g7 = 4.363, P = 0.016), with 
natural areas supporting significantly lower vegetation 
cover than either the areas around oil-pads (P = 0.027) 
and along roads (P = 0.006); vegetation cover did not 
differ significantly between oil-pads and along roads. No 
other difference was detected within habitat LI. In both 
habitats L3 and L7, there were no significant differences 
in vegetation measurements across the three areas. In 
habitat VI, there was significant variation in the number 
Percent Vegetation Cover 
Figure 1. Relationship between mean percent vegetation cover in habitats and the density of Spinifexbirds. The correlation is statistically 
significant (see text). 
105 
