Wednesday, August 7, 2013

Hillarys Pelagic Trip Report - 4 August 2013

Participants: Alan Collins (Organiser), John Graff (Organiser), Sue Abbotts, Ben Allen, Steve Burns, Wes Cooper, Cheryl Davis, Alison Gye, William Gye, Murray Hennessy, Mark Henryon, John Litherland, Josan Moss, Clive Nealon, Simon Nevill, Diego Pitzalis, Jill Rowbottom, Georgina Steytler

Conditions: Winds were forecast to be north-westerly at less than 10knts during the morning increasing to 15-20knt as the day progressed. Seas were forecast up to 2m, with a swell of 1m. Conditions on the day were roughly as forecast. Sea temperatures were in the range of 20-21 degrees Celsius.

Report: This trip produced a fairly standard variety of species, however overall numbers were low, with the notable exception of Soft-plumaged Petrels. The low numbers of Indian Yellow-nosed Albatross was a surprise for this time of year, and the complete absence of Hutton’s Shearwater even more so as August is generally the peak passage time for the species off the south-west coasts (they had been recorded on all ten previous Hillarys Pelagics in August).

Cape Petrel, race australe (Snares Cape Petrel). Note the relatively limited white in the upperwing, particularly the extensive dark division between the two white patches.

There were early issues when the deckhand failed to turn up, and it wasn’t until 0800 that we were able to board the boat and set off. A couple of Pacific Gulls were seen around the harbour during the wait. Conditions were calm inshore and apart from a few coastal species near the harbour, things were extremely quiet until we passed west of the west end of Rottnest. The only birds seen on the way out up until that point were an Australasian Gannet and a group of Crested Terns (all at the same time). As we continued west of Rottnest, a Little Shearwater off the port side, followed a short while later by a second, more distant individual. Unfortunately as usual, they quickly continued on their way and only a few people saw either bird. Shortly afterwards, the first White-faced Storm-Petrel was seen, followed by several Soft-plumaged Petrels. We finally saw a single Indian Yellow-nosed Albatross – their absence until that point was surprising as the first birds are usually seen as we reach the Rottnest line along. More Soft-plumaged Petrels and a second Indian Yellow-nosed Albatross were the only further birds seen before we stopped the boat in 400m of water and deployed the chum mix, though two Humpback Whales were seen relatively close off the stern.

Soft-plumaged Petrel, the most common species on the day. Photo courtesy Clive Nealon.
A few Soft-plumaged Petrels arrived shortly after the chum hit the water, followed by a single Wilson’s Storm-Petrel, then a White-faced Storm-Petrel. However, overall activity was low and bird numbers built very slowly. The first Indian Yellow-nosed Albatross arrived, with numbers subsequently building to five – a particularly low number for this time of year – and was followed by the first Great-winged Petrel. We had drifted east a little, and repositioned near the start of the slick. The same species remained in attendance, but were joined by a Cape Petrel. This bird was an interesting individual as the relatively limited amount of white in the upperwing strongly indicated this bird represented the subspecies australe (Snares Cape Petrel), which breeds on New Zealand subantarctic islands. This subspecies is substantially less common than the nominate capense, estimated to make up less than 5% of the overall Cape Petrel population (see Shirihai The Complete Guide to Antarctic Wildlife). Indeed, it is reportedly often less common than the nominate race even in coastal New Zealand waters in the breeding season (see Onley & Scofield Albatrosses, Petrels & Shearwaters of the World).

Young Indian Yellow-nosed Albatross (note all black bill for age). Normally a very common species in August, the count for this trip was very low. Photo courtesy Murray Hennessy.

The same species remained around the boat, with all being present in low numbers except for Soft-plumaged Petrel which continued to be the most common species in evidence. As a result, it was no surprise when a dark morph Soft-plumaged Petrel (or dark intermediate morph, depending on your definition of the morphs in Soft-plumaged Petrel!) appeared. Intermediate and dark morph individuals are rarely seen in general (extremely rarely in the case of true intermediate birds), however they appear to be more common in the eastern Indian Ocean, including off the WA coast. Next up was a distant giant-petrel which was called off the starboard side. Fortunately it was drawn to the chum and approached the boat, landing in the slick near the boat. This allowed us to confirm its identity as a Southern Giant-Petrel – a very young bird only just beginning to show the diagnostic green bill tip.

Soft-plumaged Petrel, dark morph (or arguable dark intermediate morph). Photo courtesy Clive Nealon.
Southern Giant-Petrel, a very young bird with only the first traces of the green bill tip showing. Photo courtesy Clive Nealon.

Shortly afterwards, we moved south along the 400m contour for 20 minutes searching for more birds. However, the bird action remained quiet – similar species were recorded at this new stop, with Soft-plumaged Petrels again the most common species. Another Cape Petrel appeared, this one with more intermediate amount of white in the upperwing. However, nothing new appeared and we had to turn for home. Shortly after we started moving, a Brown Skua appeared in the wake, the first for the day. Aside from that, the return journey produced nothing new, though another Brown Skua was seen closer to shore, and Soft-plumaged Petrels continued to be the most common species until we passed Rottnest. More Australasian Gannets were also in evidence on the return, and a few people saw a couple of distant Little Shearwater. The highlight was probably a mother and calf Humpback Whale seen tail-slapping north of Rottnest – several other Humpbacks were also seen distantly during the return journey. We docked at around 1615, picking up another Pacific Gull as we entered the harbour.

Humpback Whale tail-slapping, with Soft-plumaged Petrel in shot.
Many thanks, as always, to all the participants who make these trips possible. Thanks also go to the skipper for his efforts throughout the trip. No thanks though to the unknown deckhand who failed to show!

Species List [Total Count (Maximum no. seen at one time)]
Indian Yellow-nosed Albatross 12 (5)
Southern Giant-Petrel 1 (1)
Cape Petrel 2 (1) – 1 race australe (Snares Cape Petrel)
Great-winged Petrel 7 (1)
Soft-plumaged Petrel 70 (12) – 1 dark (or dark intermediate) morph
Little Shearwater 4 (1)
Wilson's Storm Petrel 4 (1)
White-faced Storm Petrel 9 (3)
Brown Skua 2 (1)
Australasian Gannet 15 (6)
Crested Tern 16 (8)

Humpback Whale 9 (2)

In harbour (not complete list!)
Pacific Gull 3 (1)

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