Breeding biology of the Flesh-footed Shearwater (Puffinus carneipes) on Woody Island, Western Australia

Brief description

The breeding biology of the Flesh-footed Shearwater on Woody Island, Western Australia was studied between 2000 and 2003. The density of burrows, burrow-length, soil-depth, attendance, laying, incubation, hatching, nestling growth and breeding success were measured to provide valuable data on this little studied bird.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: We studied the breeding of Flesh-footed Shearwaters at Woody Island between 2000 and 2003, from the time adults returned to the colony after migration, in late-September, to the departure of the last fledglings, early in May the following year. Densities of burrows were calculated at the three known breeding sites by counting burrow entrances in three, two and two 2m-wide transects at each site respectively. Lengths of transects varied, with burrows counted from the first burrow encountered nearest the sea to the last burrow encountered up-slope. Because the breeding areas were discrete and widely separated in relation to the size of the eastern headland, it was suspected that the habitat available for burrowing was restricted by the depth of the soil. To investigate this, the lengths of burrows were measured against a scale marked on a burrow-scope used for visual examination of nests (Dyer and Hill 1991). After all fledglings had left, depth of soil was measured using a sharpened spring-steel probe. Measurements were taken in 2m2 quadrats marked out at intervals of 5 m along additional transects in the three breeding sites (referred to hereafter as sites A, B and C), as well as in one larger, similarly vegetated area. This area (site D) had no evidence of shearwater burrowing, but superficially resembled the other sites (i.e. it was the only other area on the island dominated by Berry Saltbush). The mean of five penetrations made at the quadrant corners and at the centre point was determined (Neil and Dyer 1992) together with the aspect of the quadrat and its gradient, estimated as slight (<10 degrees), medium (10-40 degrees) or steep (>40 degrees). As with burrow-density transects, these soil-depth transects began at the limit of the vegetation nearest the sea, and finished upslope where it gave way to either eucalypt forest or bare granite. Sites A and B faced south and both had a medium gradient. Site C faced north and had a slight gradient, whereas site D faced north and had a medium gradient. From around mid-October, all burrows accessible without the removal of vegetation (the number of which varied from year to year) were individually numbered, and activity was monitored daily using wooden pop-sticks as knockdown barricades. Many burrows numbered during the first year of the study were used throughout the study, but new ones were dug in consecutive years and were subsequently numbered. From mid-November, when laying began, until it ended in mid-December, each active burrow was visually examined daily using a burrow-scope (Dyer and Hill 1991) to detect the presence of an egg. In late 2002, at 16 nests accessible with minimal disturbance, one member of each incubating pair was marked on the forehead with a spot of non-toxic paint. This provided a long-lasting means of identification which, by burrow-scope, enabled each prospective parent to be distinguished from its partner. All marked adults were weighed, measured, and banded. A sample of 40 adults was also weighed just before the pre-laying exodus. While no incidences of nest desertion were detected during these operations, handling of incubating birds and eggs was otherwise avoided. Daily burrow-scope monitoring resumed in mid-January to determine hatching. In each year at 20 nests, incorporating all three breeding areas, the chick was weighed daily from the time it was left alone in the nest until it left the burrow permanently. Chicks were accessed either by reaching into the nest-chamber from the burrow entrance or through a hatch dug into the burrow close to the nest-chamber. Weights were recorded to the nearest gram up to 100 g, and to the nearest 5 g when >100 g. Each week every chick had its head-length, bill-length, bill-depth and tarsal length measured to ±0.1 mm with vernier calipers. The headlength was measured from the tip of the maxillary unguis to the rear of the skull, and the bill-length from the tip of the maxillary unguis to the edge of the exposed culminicorn. Bill-depth was measured vertically at the nares, and tarsal length was taken as the length of the tarsometatarsus. Wing-length was measured to the nearest 1 mm using a stainless-steel stopped rule, measuring the maximum flattened chord of the metacarpal, excluding down, to the longest developing primary feather. ***Reference***Dyer, P. K., and Hill, G. J. E.(1991). A solution to the problem of determining occupancy status of Wedge-tailed Shearwater Puffinus puffinus burrows. Emu 91, 20-25.

Notes

Purpose
To obtain data that will allow for better management of the Flesh-footed Shearwater.