Pterodroma (brevipes) magnificens, 1856

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 : 230-231

MAGNIFICENT PETREL Pterodroma (brevipes) magnificens

All except one of our sightings of Magnificent Petrel were south of Vanua Lava, Banks Islands, northern Vanuatu, where it apparently breeds ( Bretagnolle & Shirihai 2010, Tennyson et al. 2012). 7 January—42 birds over the deep waters enclosed to the west by the islands of Malekula and Espiritu Santo, and to the east by Pentecost and Maewo. 8 January—four birds during the morning approach to Vanua Lava. 9 January—one close to Vanua Lava late evening. Photographs show birds in fresh plumage. No other Cookilaria were seen during the expedition.

Collared Petrels were categorised into four plumage-types by Watling (1986), illustrated with photographs in Bretagnolle & Shirihai (2010: 294). Using the latter, Magnificent Petrels are mainly ‘dark grey’ (darkest category), with some paler below and categorised ‘smoky’ ( Bretagnolle & Shirihai 2010: 287). Most of our birds were ‘dark grey’ with a minority ‘smoky.’ None were of the paler types ‘grey peppering’ or ‘pure white’.

Bretagnolle & Shirihai (2010: 293) reported 180 Magnificent Petrels during their expedition to the Banks Islands in December 2009. They were mainly ‘dark grey’ (c.90%) with the rest ‘smoky’ (c.10%). On 24 April 2014, an expedition cruiser crossed the same deep waters between Malekula and Espiritu Santo on the one hand, and Pentecost and Maewo on the other. A squall pushed a group of c.20 Magnificent Petrels across the ship’s bow. Again, most were ‘dark grey’ with the rest ‘smoky’ (C. Collins in lit. 2017). The palest ‘smoky’ individual ( Fig. 3 ) stood out from the rest of the group. Concentrations of entirely dark-morph birds (‘dark grey’ and ‘smoky’) in December 2009 (180), in April 2014 (c.20) and in January 2017 (46) point to a distinct population.

Bretagnolle & Shirihai (2010) described Magnificent Petrel as a race of Collared Petrel P. brevipes , based on its smaller size, monomorphic plumage and timing of breeding. They stated that the vast majority of their December 2009 birds were juveniles and therefore concluded that Magnificent Petrel must breed in the austral summer, or earlier (criteria for ageing not given). Elsewhere, Collared Petrel typically breeds in the austral autumn / winter (mainly March–August, and could look quite fresh in December), is not known to breed year-round, and largely disperses from the breeding colonies ( Watling 1986).

However, taxon status for Magnificent Petrel was contested by Tennyson et al. (2012). They questioned the presence of a larger and paler bird, collected concurrently with the type series of P. b. magnificens, which Bretagnolle & Shirihai (2010) considered to be a visiting P. brevipes . Its inclusion makes the Vanua Lava population more like other populations of Collared Petrel; it increases the biometric mean values and points to polymorphism. Tennyson et al. (2012) visited Vanua Lava in March 2011. At night they captured two birds with similar biometrics, one ‘dark grey’, the other ‘paler’ (flashlight photographs in Tennyson et al. 2012: 43). They presented this as evidence that pale birds can be the same size as Magnificent Petrel. Despite the particularly strong flashlight on the paler bird, it shows a grey wash to the underparts, perhaps sufficient to qualify as ‘smoky’.

Tennyson et al. (2012) also reported that paler birds seen in the spotlight encompassed the three paler morphs of Collared Petrel. Accordingly, they concluded that the Cookilaria breeding on Vanua Lava is Collared Petrel, with a higher proportion of dark-morph birds than other colonies, and that the birds observed by Bretagnolle & Shirihai in December 2009 were fresh adults ready to breed in the austral autumn / winter, as at other colonies of P. brevipes . In our experience, interpreting plumage shades in a spotlight is subjective and potentially unreliable. We prefer to restrict our comments to specimens and wellphotographed birds. However, sightings at the colony on Vanua Lava in March (autumn) is within the main breeding period of Collared Petrels elsewhere.

During our visit to Vanua Lava on 8–10 January, just one bird was seen near the breeding island, in the evening, and there was no other sign of birds returning to the colony. We spent three afternoons and evenings north-east of Vanua Lava at the December 2009 ‘hotspot’ for Magnificent Petrels (H. Shirihai in lit. 2017) and Vanuatu Petrels P. (c.) occulta ( Bretagnolle & Shirihai 2010: 139) .

One explanation is that conditions for returning to the colony were less favourable during our visit, given calm weather and an 81–85% waxing moon (although a fair number of Vanuatu Petrels were seen, see below). Bretagnolle & Shirihai experienced more favourable conditions, with a new moon becoming a c.50% waxing moon. However, our visit was c.1 month later than that by Bretagnolle & Shirihai. Thus, if their birds were juveniles, then our visit may have followed post-breeding dispersal.

Figures

Figure 3. Presumed Magnificent Petrel Pterodroma (brevipes) magnificens, between Malekula and Espiritu Santo Islands, and Pentecost and Maewo Islands, Vanuatu, 24 April 2014 (Kirk Zufelt). Rather distant when photographed, this is the palest bird of 60 seen in these waters in April 2014 and January 2017. This individual is a shade lighter than the palest Magnificent Petrel in Bretagnolle & Shirihai (2010: 294, Fig. 8). Bretagnolle & Shirihai stated that the bird in their Fig. 8 was borderline between ‘dark grey’ and ‘smoky’, thus we label this bird ‘smoky’. Bretagnolle & Shirihai (2010: 291, Table 2) scored Magnificent Petrels at sea off Banks Islands, Vanuatu, and found that 10.53% were smoky (the rest extreme / dark grey); they scored the type series from the same waters and found 20% were smoky (the rest extreme / dark grey).