Puffinus heinrothi

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 : 233-235

HEINROTH’S SHEARWATER Puffinus heinrothi

The locations of our sightings correspond with suspected breeding on Rendova and Kolombangara Islands, Solomon Islands, and on Bougainville Island, Papua New Guinea ( Harrison 2014; Fig. 1 ). We observed five at sea: 17 January—one in Vella Gulf, between Kolombangara, Ghizo and Vella Lavella Islands; 18 January—two singles off the Shortland Islands, Solomons; 19 January—two singles c. 65 km west of the north-west end of Bougainville Island. The rest of our sightings involved singles and small groups in the Blackett Strait, a narrow oceanic passage between the islands of Kolombangara and Kohinggo, Western Province, Solomons ( Fig. 6 ). We found Heinroth’s Shearwaters strongly associated with sizeable mixed feeding and rafting flocks of noddies and terns (as did Cheshire 2010 and Harrison 2014). Flocks went into frenzies over feeding tuna that pushed bait fish to the surface. Fish activity during our visit occurred mainly early to mid-morning, and mid-afternoon to late evening ( Gibbs 1996 also noted evening activity off Kolombangara), but may have been influenced by tidal flows. We made the following sightings in Blackett Strait: 17 January—two at c.12.00 h as we motored en route to New Ireland; 25 January—having just returned from New Ireland, four in the evening; 26 January—at 07.30–09.30 h 6–8 birds, then 15.30–17.45 h 10–12, c. 16 in total. 27 January—at 07.30–09.30 h 6–8 birds, not searched for in afternoon; 28 January—at 07.30–09.30 h 6–8 birds, then 15.30–17.30 h 8–10, c. 14 in total; 29 January—at 07.30–10.30 h 16–18 birds, not searched for in afternoon; 30 January—at 07.30–11.30 h 6–8 birds, none in afternoon (also no noddies or terns); 31 January—at 07.30–11.30 h 6–8 birds, then disembarked Sauvage. There was some turnover in Blackett Strait. For example, on 26 January the majority were pale morph, whereas on 28 January approximately the same number of birds were seen but most were dark morph. Some, recognisable by a distinct marking, or by wear or moult in the primaries, were seen only once. We estimate a total of 30–50 in Blackett Strait.

On 20–25 March 2013, Harrison (2014) observed flocks of 1–25 birds, usually 50–60 per day in Vella Gulf adjoining Blackett Strait . On 21 September 2015, P. Sweet (in lit. 2017) saw 25 simultaneously in the adjoining Fergusson Passage. There were fewer birds present during our January expedition compared to the March and September visits.

Our photographs reveal a range of wear and moult in the flight feathers. Few birds had fresh plumage. Most showed light to moderate wear, the most worn feathers often being the central tail feathers, and the tail was heavily abraded in one individual. At least one bird showed moult contrast in a full set of secondaries. The only bird in active primary moult had old, worn and bleached pp8–10, with moult ongoing in the middle primaries ( Fig. 7 ). Accordingly, the birds could have been a mix of immatures and adults, given a fixed breeding season (e.g. January / March–August / September); or largely / all adults, given a protracted season.

That said, the breeding season of Heinroth’s Shearwater is barely known. No egg or nest has ever been found ( Pikacha & Sirikolo 2010, Harrison 2014). Including our sightings, there are documented records offshore from suspected breeding islands in January, March, April, July, August and September ( Hadden 1981, Gibbs 1996, Tarburton 2009, 2017, Harrison 2014; C. Collins in lit. 2017, P. Sweet in lit. 2017). Two records on Bougainville are consistent with a regular breeding period ( Hadden 1981: 23). A fledgling was found in August near the sea at Arawa, probably on its first flight. Nearby, inland at Panguna, an adult was found in July, probably en route to or from its nest. Significantly more birds in Vella Gulf in March 2013 ( Harrison 2014), compared to Vella Gulf and Blackett Strait in January 2017, may mark the period of return to the breeding grounds (January–March). Thus breeding could occur January / March–August / September. Consistent with this is evidence of dispersal to Sulawesi, Indonesia, in October–March (at least). Sightings include flocks of 70+ off Taliabu (November 2012) and 209 north of Mangole, Sula Islands (March 2017) documented by photographs and video ( Eaton et al. 2016; J. del Hoyo, J. Eaton, R. Hutchinson in lit. 2017).

Out of synch with the above timing, however, is the type specimen, a fledgling collected in New Britain on 27 May 1901 ( Heinroth 1902). If our moulting bird was a juvenile in its second pre-basic moult, then it too may have fledged May / June. Fledglings in May / June and August would point to a protracted breeding season, with one or more egg-laying peaks .

The feeding behaviour that we observed was much as described by Shirihai (2004) and Harrison (2014). Finally, we witnessed an immature White-bellied Sea-eagle Haliaeetus leucogaster make a failed attempt to predate a lone Heinroth’s Shearwater on the sea. The shearwater avoided capture by diving ( Fig. 8 ). We were surprised to observe White-bellied Sea Eagle as Sanford’s Sea-eagle H. sanfordi replaces it in the Solomons (identification substantiated in Wilson et al. in prep.).

Figures

Figure 1. Map of the route followed by Sauvage January 2017. Departed Port Vila, Vanuatu, morning of 6 January, travelled to the Banks Islands, northern Vanuatu, arriving at Vanua Lava at noon on 8 January. Departed Vanua Lava at dusk on 10 January, then travelled to Western Province, Solomon Islands, arriving at Noro, Kohinggo Island, 16 January. Departed Noro late morning on 17 January passing through Blackett Strait, then to New Ireland, Papua New Guinea, arriving at Silur Bay early morning 20 January. Departed mid-morning 22 January, returned to Western Province, Solomon Islands, arriving at Vella Gulf at dusk 24 January. Repeatedly cruised Blackett Strait until disembarking at Gizo Island early afternoon 31 January (also visited Vella Gulf and Fergusson Passage).

Figure 6. Map of the study area for Heinroth’s Shearwater Puffinus heinrothi showing Blackett Strait, Vella Gulf and Fergusson Passage.

Figure 7. Moulting Heinroth’s Shearwater Puffinus heinrothi, Blackett Strait, between Kolombangara and Kohinggo Islands, Solomons, 29 January 2017; outer three primaries old and moult ongoing in middle primaries (Kirk Zufelt)

Figure 8. An immature White-bellied Sea Eagle Haliaeetus leucogaster attempting to predate a lone Heinroth’s Shearwater Puffinus heinrothi on the sea, Blackett Strait, between Kolombangara and Kohinggo Islands, Solomons, 27 January 2017 (Kirk Zufelt)