VOL. 11 (7) SEPTEMBER 1986 213

AUSTRALIAN BIRD WATCHER 1986. II. 213-21 7

A Sighting of the Westland Petrel Procellaria westlandica off North-west Tasmania

By KEVIN BARTRAM, 58 Marine Parade, Elwood, Victoria 3184

Summary Between 4 and 18 April 1984, I took part in a cruise aboard the CSIRO oceanographical

research vessel 'Sprightly'. The ship departed Hobart on 4 April and sailed north along the east Tasmanian coast to Bass Strait We then headed west through Bass Strait to the King Island region. Much time was spent performing oceanographical surveys over inshore waters around western Bass Strait, King Island, Cape Otway, and in deep waters off those regions before arriving in Melbourne on 18 ApriL During this period I observed many seabirds including the first Westland Petrel Procell aria westlandica for north-west Tasmania.

Details of sighting On 17 April, whilst performing stationary oceanographical surveys off

north-west Tasmania (39° 42'S, 143° 07'E), a Westland Petrel approached the vessel on three occasions between 1655 and 1725 hours. Great-winged Petrels Pterodroma macroptera accompanied it, allowing comparative views of both species in differing light conditions. When in view the petrel circled the ship, obviously attracted by the large flock of birds that had gathered around. However, it was never actually seen to feed on the scraps thrown overboard as did the various other species of seabirds attending us. The Westland Petrel was observed for approximately 15 minutes in totaL Best views were obtained on the first occasion it neared the ship when the bird approached to within 40 metres and, as light conditions were quite good, I was able to accurately judge fine points such as the distribution of black on the bilL During subsequent sightings the light had deteriorated so less detail could be seen of the bill and other features. The last time I saw the bird it was chased off by three Great­winged Petrels.

Environmental conditions and other relevant details noted at the time of observation were as follows: depth 200 metres; skies partly cloudy; light good early on, deteriorating as the afternoon progressed; seas moderately rough; 20-25 knot westerly wind.

Other species present at the time were the following: eight Wandering Diomedea exulans, 20 Shy D. cauta, 50 Black-browed D. melanophrys (30 race melanophrys and 20 race impavida) and four Yellow-nosed Albatrosses D. chlororhynchos, 30 Great-winged Petrels, five Sooty Shearwaters Pu.ffinus griseus, ten Wilson's Oceanites oceanicus, one White-faced Pelagodroma marina, and seven Grey-backed Storm-Petrels Garrodia nereis, one Australasian Gannet Morus serrator and one South Polar Sku a Catharacta maccormicki (details of skua record in prep.).

This observation represents my only field experience with the Westland PetreL At the time of sighting however, I had prior field experience with eight

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White-chinned Petrels Procellaria aequinoctialis including four seen prior to this sighting on the same voyage, and one Black Petrel P parkinsoni (off Sydney), so I was familiar with the field characters of the other two dark Procellaria species. Since this sighting I have seen a further ten White-chinned Petrels and five more Black Petrels.

Description The following description is based on field notes and sketches made at the

time of the sighting. General impression was of a very large petrel, obviously much smaller than

a giant-petrel Macronectes. I could make direct size comparisons with nearby Great-winged Petrels: it was at least a third larger in wingspan, and nearly twice as large in body bulk. Size, shape, and jizz very similar to White­chinned Petrel.

This bird was large and bulky in body shape, and generally more solidly built than Black Petrel. Its head was very large, neck thick, and back bulky giving it a hunch-backed appearance compared to the relatively sleek appearance of Black Petrel. Wings were long and slender, and held fairly straight. The wedged-shaped tail was often fanned out, and typically very short as in all Procellaria. Feet, when fully extended, trailed a few centimetres beyond the tail tip.

Bill was bulky, horn-coloured, almost white. (The bill gave me the impression of being more slender in profile than the bulkier bill of the White­chinned Petrel, though similar in length. Black Petrel has a smaller, shorter bill in proportion to head size.) Nostrils pale, bordered by black naricorn. Culmen black. Maxillary unguis also black, except for a pale patch at the sides of its basal third. Mandibular unguis all black. Latericorn and rami corn all whitish horn apart from the black sulcus.

Iris dark, legs black. Body wholly black with a brown tinge. Blacker in colouration than nearby

Great-winged Petrels. No white chin. Upperwings black apart from the outer two primaries and their coverts, which were more brown due to wear. Underwings black with a silvery appearance to the bases of the primaries caused by reflection.

The two outer primaries and their coverts were old and very brown. A large gap separated the two old outer primaries from the new inners which were black. Probably about two or three primaries short or missing, causing the gap. Did not see rest of plumage well enough to ascertain amount of moult or wear if any.

In the strong winds it flew with much arcing and gliding, occasionally interspersed with intermittent rapid flapping.

Diagnosis The large size, general shape, short tail, large bulbous bill and black feet

easily identify this species from Flesh-footed Shearwater Puffinus carneipes. The only serious identification contenders are the black-plumaged members of the genus Procellaria.

VOL. 11 (7) SEPTEMBER 1986 Sighting of Westland Petrel off N-W Tasmania 215

Figure 1. Sketch of Westland Petrel Procellaria westlandica observed off north-west Tasmania, 17 April 1984: bill pattern (left), dorsal surface showing primary moult (right).

Drawing: Kevin Bartram

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White-chinned Petrel often has a very small black patch along the inner cutting edge of the maxillary unguis (pers. obs.), which is virtually impossible to see in the field. This is in contrast to Westland Petrel in which the bill pattern varies from a completely black maxillary unguis, to at least some black on the bill tip, always more extensive than White-chinned Petrel (Harrison 1983). The Procellaria I saw had a black maxillary unguis with pale sides confined to the basal third. Apart from the black bill tip which in itself is diagnostic, this bird lacked a white chin. Otherwise it was quite similar to a White-chinned Petrel in overall appearance.

Black Petrel has a very similar bill pattern to Westland Petrel, thus separation from Black Petrel relies mainly on size, and to a lesser degree on body shape. In size, shape and jizz, the bird I saw was very similar to White­chinned Petrel. Compared to nearby Great-winged Petrels it was about one third greater in wingspan, and about twice as large in body bulk. This is certainly larger than Black Petrel, a species only slightly but noticeably larger in wingspan and body size than Flesh-footed Shearwater, which is similar in size to Great-winged Petrel. To reinforce the above size comparisons, the following is a list of wing lengths from Serventy et al. (1971): Great-winged Petrel av. 309 mm (range 304-317); White-chinned Petrel 372 (339-409); Westland Petrel 377 (366-390); Black Petrel 343 (326-359); Flesh-footed Shearwater 309 (294-317). On a size scale, in my experience, Westland Petrel and White-chinned Petrel would be the largest, Black Petrel would fit in the middle and at the end of the scale would be Great-winged Petrel and Flesh­footed Shearwater.

The similarity of Westland and White-chinned Petrels in shape and the differences between the latter two and Black Petrel were pointed out to me before this sighting in personal communication with D. W. Eades. Study of photographs taken by D. W. Eades, M. J. Carter and C. Corben and personal observations at sea confirm his ideas. Westland Petrel like White-chinned Petrel is a very bulky bird, more solidly built than Black Petrel. In the former two species the head is large, neck thick, and the back is bulky, giving a hunch-backed appearance. This contrasts with the sleekness of the Black Petrel. In proportions the Procellaria I observed appeared identical to White­chinned Petrels seen earlier this trip, and was obviously different in shape from the Black Petrels I have seen off Sydney before and since.

Another difference noted between the bird and Black Petrel was the larger bill. In specimens I have studied in the Australian Museum collection, both White-chinned Petrels and Westland Petrels have larger bills than Black Petrel. This can be illustrated by culmen measurements in Serventy et al. (1971): White-chinned Petrel av. 52 mm (range 48-56); Westland Petrel49 (47-51); Black Petrel42 (39-44). This agrees with what I saw in the field; the bill size and shape of this bird was far closer to that of a White-chinned Petrel than to the smaller and stumpier bill of Black Petrel.

This bird was in heavy wing moult. According to Bartle (Roberson 1985: 91), adults complete wing moult by April. As this bird was still in heavy primary moult on 17 April it is likely that it was an immature or sub-adult.

Full details of this sighting were submitted to the Records Appraisal Committee of the RAOU. The record was unanimously accepted (T. R. Lindsey pers. comm.).

VOL. 11 (7) SEPTEMBER 1986

Brief summary of status

Sighting of Westland Petrel off N-W Tasmania 217

There are no prior records of this species for the north-west region of Tasmania. However, there are other records for south-east and eastern Tasmania. Carter (1981) has summarised his personal sightings along with those of other observers between April and May 1979 off south-east Tasmania. A total of four were recorded within that period. D. W. Eades and J. L. McKean (pers. comm.) also reported sightings of this species off south­east and eastern Tasmania between March and September. Additional published records of this species for Australia all concern beachwashed specimens from New South Wales. Single birds from central New South Wales were found on 2 January 1956 (Corrimal Beach), 12 December 1958 (Cronulla Beach) (McGill 1959) and 1 January 1976 (Kingscliff) (Vernon 1977). An additional specimen was found on Boambee Beach on 14 December 1976 by Glenn Holmes (Gibson 1977). The above records suggest that the Westland Petrel could be a regular visitor to south-eastern Australian seas in small numbers.

Acknowledgements I wish to thank the CSIRO, Victorian Institute of Marine Sciences and the

Captain and crew of'Sprightly' for allowing me to participate in their cruise. I would also like to acknowledge D. W. Eades, T. A Reid and J. Zimmerman for their comments on this paper.

References Carter, M. J. (1981), 'Seabird observations off south-east Tasmania', Australasian Seabird

Group Neswl. 15, 9-10. Gibson, J. D. (1977), 'Birds of the County of Camden (including the Illawarra district)', Aust

Birds 11, 48. Harrison, P. (1983), Seabirds, An Identification Guide, Croom Helm, Kent. McGill, A R (1959), 'The Westland Petrel: a second Australian occurrence', Emu 59, 259-

264. Robertson, C. J. R (1985) (Ed.), Reader's Digest Complete Book of New Zealand Birds, Reader's

Digest Services, Sydney. Serventy, D. L., Serventy, V. & Warham, J. (1971), The Handbook of Australian Seabirds, Reed,

Sydney. Vernon, D. P. (1977), 'The first live Australian specimen of the Westland Petrel Procellaria

westlandica', Aust. Bird Watcher 7, 44-46.

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