Pruett-Jones & O'Donnell: Land Birds on Barrow Island 
that we counted all birds using the quadrats. In areas 
with continuous and dense spinifex, the spinifexbird was 
sometimes difficult to detect because it often hid within 
large spinifex plants. In such situations, it was possible 
that we missed a few individual spinifexbirds although 
we made every effort possible to detect all individuals 
present. 
We calculated total population estimates for all 16 
species recorded on transects (see Results). The estimates 
were made as follows: (population density in each 
vegetation zone)/(proportion of total area of each zone 
that was surveyed during quadrat transects), summed 
over all vegetation zones = total population estimate. 
Besides conducting transects in natural, undisturbed 
areas, we also carried out a census of birds around oil 
pads (the raised or leveled areas on which there was a 
Lufkin oil pump) and also along roads. The oil pad and 
road censuses were conducted as described above, with 
the following exceptions: first, the oil pad quadrats 
consisted of abutting rectangles at right angles to each 
other (either two or three, two ha total area) that were 
oriented so that they surrounded the oil pad; and second, 
the road side quadrats consisted of two areas 200 m long 
x 50 m wide (two ha total area) on either side of the road. 
For the roadside transects, censuses were carried out in 
both areas on either side of the road simultaneously, with 
each of us walking along a mid-line of the quadrat. The 
oil pad and road transects were conducted in four 
vegetation zones as follows: LI (hummock grassland of 
T. wiseana with Ficus platypoda on central limestone 
ridges); L3 (hummock grassland of T. wiseana with low 
mixed shrubs including A. gregorii on limestone ridges); 
L7 (hummock grassland of T. wiseana with dense pockets 
of M. cardiophylla on limestone ridges); and VI (hummock 
grassland of T. wiseana with mixed emergent shrub 
species on valley slopes). These four habitats were chosen 
because they were the most common habitats on the 
island and because the majority of oil pads and roads 
associated with the oil-field development were located in 
these habitats. 
We took vegetation measurements on each quadrat to 
quantify large-scale differences between vegetation types. 
At the starting point of each transect, and at every 50 m 
(5 points total) we measured vegetation cover and 
vegetation height. Vegetation cover was measured at 
ground level and was scored as the number (percentage) 
of 1 cm squares of a 1 m long stick that was covered by 
living vegetation. In addition, for the entire quadrat as a 
whole, we measured the height of the tallest tree or shrub 
(maximum vegetation height) and also counted the 
number of emergent shrubs. Emergent shrubs were 
defined as woody shrubs that were at least 50% taller 
than the surrounding vegetation. This relative measure 
was necessary because the height of the spinifex, which 
covered the ground in most areas, varied greatly in 
height (e.g., from 0.3 m for T. wiseana to 1.5 m for T. 
angusta). The number of emergent shrubs was scored as 1 
(0 emergent shrubs), 2 (1-10 emergent shrubs), 3 (10-25 
emergent shrubs), 4 (25-50 emergent shrubs), and 5 (50+ 
emergent shrubs). 
In addition to counting birds on the quadrats, we also 
recorded birds seen outside the quadrats during the 
formal counts, and also during general fieldwork during 
our time on the island. 
Results 
Avifauna 
During transects, 777 individuals of 16 species were 
recorded. Two additional species, the Black-shouldered 
Kite and Richard's Pipit (see below) were observed 
during general fieldwork, but not recorded on transects. 
An assessment of the status of each of these 18 species is 
presented below. Our definitions of status is: common = 
an abundant species (>10 individuals recorded on 
quadrats), seen in many habitats across the island; 
uncommon = a species only occasionally seen (3-10 
individuals recorded on quadrats), or restricted to 
specific habitats; rare = a species for which just a few 
individuals were seen (1-2 individuals recorded on 
quadrats), and/or a species that was restricted to just one 
or two habitat types. 
• Spotted Harrier ( Circus assimilis): Uncommon; 
individuals occasionally seen inland; scattered along 
coast. 
• Brahminy Kite (Haliaster indus): Rare; pairs 
occasionally seen inland off the quadrats; scattered 
along coast. 
• Osprey ( Pandion haliaetus): Rare on quadrats; pairs 
regularly spaced around coastline; not seen inland 
but we received reports that individuals will cross 
the island (W. H. Butler, pers. comm.). All 
individuals we recorded were seen within 1 km of 
the coastline. Nesting pairs were observed using 
both natural sites and nesting platforms erected by 
WAPET. 
• White-breasted Sea-Eagle (Haliaeetus leucogaster): 
Rare on quadrats; pairs occasional along coastline; 
not seen inland, but we received reports that 
individuals regularly hunt inland especially near 
hills (W. H. Butler, pers. comm.). Nesting pairs seen 
on southern coast. 
• Black-shouldered Kite ( Elanus caeruleus): Rare; not 
seen on quadrats; two individuals seen on island 
during fieldwork. 
• Australian Kestrel ( Falco cenchroides ): Rare; 
individuals occasionally seen inland; not seen along 
coast, although this species is known to nest on 
coastal cliffs (W. H. Butler, pers. comm.). 
• Bar-shouldered Dove ( Geopelia humeralis): Common 
in central limestone ridges in valleys, less so on flats 
and in coastal area; known to nest on limestone 
ledges, caves, in mangroves and Acacia sp. along the 
coast (W. H. Butler, pers. comm.) 
• Black-eared Cuckoo ( Chrysococcyx osculans): Rare, but 
scattered throughout island in habitats with 
emergent shrubs and trees. 
• Horsfield's Bronze-Cuckoo (C. basalis ): Uncommon, 
but scattered throughout island in habitats with 
emergent shrubs and trees. 
• Sacred Kingfisher (Todiratnphus sanctus ): Rare; only 
seen along creeks and drainage lines. 
• Welcome Swallow ( Hirundo neoxena): Common and 
widespread; common around developed areas, less 
so elsewhere. Many nesting pairs observed at camp 
and airport. 
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