Pseudobulweria becki (Murphy, 1928)

Flood, Robert L., Wilson, Angus C. & Zufelt, Kirk, 2017, Observations of five litle-known tubenoses from Melanesia in January 2017, Bulletin of the British Ornithologists’ Club 137 (3), pp. 226-236 : 227-228

BECK’S PETREL Pseudobulweria becki

At first light on 20 January, at c.06.30 h, Sauvage was c. 15 km south-east of Silur Bay in south-eastern New Ireland ( Fig. 2 ). The first Beck’s Petrel was seen c. 10 km offshore as we approached the bay. The majority of sightings over the next few days were within 5 km of shore, mainly <2 km of shore, with some just 50 m from land. The birds rarely approached closer to the vessel than 100 m. We were unable to identify any fresh juveniles among the best-seen birds. A few were in active primary moult (see below) and the rest showed some degree of wear. Sightings on 20–22 January in the vicinity of Silur Bay were as follows. 20 January —24 birds to 08.30 h flying north, then eight to 15.30 h flying north / south, and two sat in the bay, with 12 to 16.00 h flying south during a squall, ten to 18.00 h flying south, and eight birds to dusk milling around the mouth of the bay (none within it). 21 January —18 to 08.30 h flying north, then 13 flying north / south to 15.30 h and two sat in the bay, but none beyond 5 km in the direction of the Fini Islands to the east, 11.30 h to 15.30 h, then 18 and a Tahiti Petrel P. rostrata to dusk, with some Beck’s Petrels milling at the mouth of Silur Bay . 22 January —none to 08.30 h, then three to 12.30 h while motoring south to Cape St. George , followed by 12 to dusk while sailing south-southeast from Cape St. George , most within the first 15 km, none beyond 40 km.

Wind and sea conditions were calm during the first two days, with just the occasional squall descending from the Hans Meyer Range (highest peak 2,379 m). On 22 January, the wind turned north-west force 4, giving blustery conditions and a choppy sea south of Cape St. George. Beck’s Petrels favoured these windy conditions and few were seen in the lee of the island. Conditions returned to calm by early evening.

Very few Beck’s / Tahiti Petrels were seen elsewhere. 10 January— one P. rostrata off Vanua Lava, Vanuatu. 19 January—one Beck’s / Tahiti Petrel distantly c. 90 km south-east of Cape St. George. 23 January— three P. rostrata c. 100–200 km south-southeast of Cape St. George. Tahiti Petrels were seen well and fairly easily identified by size, structure and flight behaviour (see Shirihai 2008a) .

The breeding grounds of Beck’s Petrel are unknown and finding them is critical to its conservation. Concentrations off Cape St. George in July / August ( Shirihai 2008a,b) and at Silur Bay in March / April ( Bird 2012, Bird et al. 2014, Bird & Gaskin 2016) strongly suggest breeding in the nearby Hans Meyer Range. Our January sightings, mainly within or near Silur Bay, add weight to the supposition that Beck’s Petrel breeds nearby.

The above sightings are consistent with a breeding season February / March–July / August. However, the closely related Tahiti Petrel is thought to breed year-round, with egg-laying peaks varying locally ( Carboneras et al. 2017). Our sightings do not exclude this possibility for Beck’s Petrel. Although our study found fewer birds in January compared to March / April ( Bird 2012, Bird et al. 2014), some birds were loafing off Silur Bay in the evening, like active breeders. That said, other individuals were in active primary moult. Two examples photographed show outer five / six primaries old, moult ongoing among the inner five / four primaries. Procellariidae in active primary moult are unlikely to be nesting, as they usually start primary moult post-breeding. So, moulting birds could have been post-breeding adults, or immatures. Immature Procellariidae tend to disperse from the breeding grounds for several years, but dispersal patterns for Beck’s Petrel are unknown.

Figures

Figure 2. Map of the eastern Bismarck archipelago (including New Britain, New Ireland and Bougainville), showing localities mentioned in the text, and the locations of our and Shirihai’s (2008a) sightings of an unidentified all-dark Pseudobulweria.