An investtgat1on into the association between covered burrow entrances and the breeding status
of occupants of burrows was prompted when Wedge-tailed Shearwaters were seen covering the
entrances to their burrows. The results showed that neither covered nor cleared entrances should be
used as indicators for occupied breeding burrows. Burrows with covered entrances may contain
incubating birds, and those with cleared entrances may only be used at night by immature birds. The
incidence of burrows with covered entrances was related to habitat type which influenced the availability
of litter and debris.

The density of nesting burrows of the Wedge-tailed Shearwater Puffinus pacificus was measured
in 224 quadrats on Heron Island, Great Barrier Reef. Field measurements of the unconfined compressive
strength of the soil material were made for each quadrat. Lowest burrow densities occurred in quadrats
at both upper and lower ends of the soil strength range. Increased burrowing success at sites where
soil is not so loose as to collapse, but not so compacted as to inhibit burrowing is indicated. lsl&nd
development which results in soil compaction may, therefore, inhibit P. pacificus nesting.

Body weights and dimensions were recorded for 70 fledglings at Heron Island, on the southern
Great Barrier Reef. Results show that the length of the longest primary feather and tarsus were
·significantly different between habitats, with the Fringe showing highest and Buildings area showing
lowest means. This outcome probably resulted from most nestlings measured in the Buildings area
being the progeny of early breeders. Variability in the breeding cycle may have confounded the
analyses of body weight and of dimensions. When data were grouped according to the timing of laying,
early breeders showed significantly lower hatching and breeding success. Both these results are useful
for detecting inter-annual differences at this locality or for comparisons with colonies located elsewhere.

Wedge-tailed Shearwater burrows were surveyed at Rocky Islet, northern Great Barrier Reef,
opportunistically during 1994, and systematically in 1995. The burrow estimate for the island was
5 785 ± 840 for the first year and 4 646 ± 302 during the second survey. The size of the breeding
population is estimated to be 2 950 and 2 369 for 1994 and 1995 respectively. Burrow occupancy
status was established during 1995 using a burrowscope, and a fledgling occupancy rate of 0.33
found. Chick development was quite advanced compared with birds from southern populations at the
same time.

The population size of the Black Noddy Anous minutus was monitored over five years at Heron
Island, a 13.5 ha coral cay located on the southern Great Barrier Reef. The population which reached
around 67 000 breeding pairs in 1989 appears to be increasing, although the rate of expansion is
difficult to determine. Highest nesting densities are found in large Pisonia grandis, probably due to
higher nesting site availability. Nesting densities appear to be independent of the degree of habitat
modification; differences in breeding success with disturbance remain to be investigated.

The breeding activities of Wedge-tailed Shearwaters at Raine Island, in the far northern section of the Great
Barrier Reef, have not been quantified to date. In December 1995, 58 per cent of burrows inspected with a
'burrowscope' were occupied, 52 per cent with incubation or a chick, so approximately half of the estimated
3 661 burrows were likely to be active, breeding burrows. There appeared to be a locational preference for nesting
on the western end of the island. Breeding rates on Raine Island were similar to those of the principal Great
Barrier Reef Wedge-tailed Shearwater colonies of the Capricorn Group of islands.

Mudjimba Island has recently been included in the Maroochy River Conservation Park. One of the factors
influencing the decision was that the island's Wedge-tailed Shearwater Puffinus pacificus colony may be the only
viable colony remaining in south-east Queensland and one of only two colonies that inhabit mainland islands in
Queensland. The colony was first described by Lane and Battam (1984, 1985) after they visited the island in
February 1984. They estimated a breeding population of between 1 500 and 2 000 breeding pairs. This paper
presents an estimate of approximately 2 700 burrows for the 1997/98 season; breeding rates of approximately
37 per cent for the 1996/97 and 1997/98 seasons; and a breeding success rate of about 84 per cent at fledgling
stage for the 1997/98 season.

In January 2001 burrow occupancy for two species of Shearwater Puffinus carneipes and Puffinus pacificus
was ascertained by using a burrowscope to inspect burrow contents at various sites on Lord Howe Island. Burrow
occupancy (and burrow lengths) for Puffinus carneipes and Puffinus pacificus averaged 60 per cent (1.4 m) and
57 per cent (0.8 m) respectively. Neither burrow density nor the amounts of litter covering burrow entrances were
good indicators of burrow occupancy.

Collecting reliable field data on breeding populations of booby species on Raine Island for temporal comparison
is challenging. This trial's aim was to establish baseline data on nest census estimates in December 1998 to
serve as the foundation for continued monitoring. Based on censuses, estimates of numbers of 3 700 Brown,
700 Masked, and 330 Red-footed Booby nests were established. Egg predation by seagulls in December 2000,
however, prevented the first replication of the study thus exposing the limitations of the method.

Between December 1995 and December 2000 there was an apparent decline of greater than 40 per cent in
the number of occupi ed Wedge-tailed Shearwater Puffinus pacificus burrows on Raine Island. The estimated census
of approximately 3 550 burrows or crevice nests in December 1995 declined to estimates of approximately 2 360
and 1 570 Shearwater burrows or crevice nests in December 1998 and 2000 respectively. Burrow occupancy was
approximately 56 per cent in 1998 and 66 per cent in 2000, with eggs or chicks found in 43 per cent of burrows
in 1998 and 49 per cent in 2000. Yet the number of occupied ledge crevice nests found in 1998 (130) and 2000
(131) was approximately double that found in 1995 (60). The overall decline may be due to turtle nesting activities
on the northern ridge however further investigation is needed to verify this.