Trip Report
Hauraki Gulf Seabirds
Trip reports for January and early February 2007
Over the past month we’ve run five Hauraki Gulf pelagics (7, 14, 21 & 29 Jan and 1 Feb) and it’s been fascinating to see the changes in terms of seabird occurrence and distribution in the outer Hauraki Gulf, as well as marked changes in environmental conditions (ie. SST, plankton presence and so forth). In addition, the changes between this latter period and previous months.
The Hauraki Gulf is best described as a large embayment bounded by the mainland (North Auckland Peninsula and Auckland Isthmus), Firth of Thames, Coromandel Peninsula and Great Barrier Island with a large opening to the north (between GBI and Bream Head) and a narrower one to the east (Colville Channel). It’s relatively shallow with a (continental) shelf environment all the way to the shelf edge approx 50kms north east of the Mokohinaus (the outermost island group which themselves are over 100kms from the Waitemata Harbour, Downtown Auckland). Compare this to Kaikoura (where the shelf edge comes to within a kilometre from shore!) or Cape Brett, Bay of Islands (approx 20kms offshore). Scattered within the Hauraki Gulf are a number of islands and island groups, significant nature reserves and hugely important for northern seabirds. There are some very interesting marine dynamics at play through the outer Gulf area and they influence where seabirds are to be found at any time, particularly those seabirds that breed on islands within the Gulf and use it as a feeding ground. Basically seabirds breed where they can, and feed where they find their food, a moveable ‘feast’. Sort of obvious, but it’s amazing what people come up with when they can’t find birds where they were reported one, two or three years ago.
So what’s been happening lately? Consider these species:
- Buller’s Shearwater (Puffinus bulleri) – common throughout the outer Gulf and concentrating in large numbers around the Mokohinaus, until 21 Jan. They feed around active schools of fish (eg trevally, kahawai, kingfish). Later in January numbers dropped away inside the Mokes but were still fairly common and widespread. Buller’s do in fact range widely around the NZ coast during summer months (I saw 20+ off Kaikoura last weekend).
- Flesh-footed Shearwater (P. carneipes) – common throughout the outer Gulf on all trips and would readily approach the boat during chumming sessions. They feed around active schools of fish (eg trevally, kahawai, kingfish) and are the most obvious scavengers around recreational and commercial fishing boats in the Gulf. Can be seen around NZ waters at this time of the year (eg Chatham Rise, Cook Strait and Kaikoura).
- Fluttering Shearwater (P. gavia) – common close to the mainland in big mobile flocks then scattered further out beyond Little Barrier Island (increasing in number near the Mokes one of their breeding sites). They feed around active schools of large fish (eg trevally, kahawai), on small fish etc.
- Fairy Prion (Pachyptila turtur) – found in large numbers in the vicinity of the Mokohinaus until 21 Jan. None seen on 29 Jan and 1 Feb. These are plankton feeders.
- White-faced Storm Petrel (Pelagodroma marina) – Two colonies 90kms apart Noises in the inner Gulf and Mokohinaus in the outer Gulf) mean that these birds are well spread throughout the Hauraki Gulf, and we found them in large numbers in the vicinity of the Mokohinaus up until 21 Jan (nothing like finding food right at your doorstep). On the last two trips however numbers fell away in the area W and NW of LBI all the way out to the Mokes, and were only in good numbers NE and SE of Little Barrier. Once again these birds feed on plankton.
- New Zealand Storm Petrel (Pealeornis maoriana) – found on all trips during January and in good numbers (up to 7 birds confirmed) at chumming sessions (no longer than an hour and half), however a significant shift in area of occurrence in the last two trips when they were found only NE of LBI. Earlier in the month they could be found at two or three different locations each trip which meant their occurrence was widespread across the outer Hauraki Gulf. Of course this is in marked contrast to November and through much of December when they were scattered in very small numbers right out to the shelf edge frustrating capture attempts. That this happened should be no great mystery and coincided with a period of cooling of outer Gulf waters (great for some species but not NZSP in terms of the outer Hauraki Gulf). Obviously these birds were feeding further afield and what they might be feeding is the subject of some intriguing debate.
- Little Shearwater (Puffinus assimilis) – seen in small and diminishing numbers through Jan reflecting an end to their breeding season and a move out of Gulf waters.
> Common Diving Petrels (Pelecanoides urinatrix) – in very small numbers early in January and absent later in the month reflecting their move out of the Gulf waters post-breeding (where do they go to?).
- Cook’s Petrel (Pterodroma cookii) – common throughout the outer Gulf until 21 Jan, but numbers dropped off markedly in the last two trips. They range as far as the Chatham Rise and known feeding grounds are off East Cape (North Island) and the Tasman Sea (we see them flying across the North Auckland mainland heading towards LBI which is their major colony). We have seen small numbers of Cook’s Petrels feeding around schools of kingfish in mixed groups of seabirds.
- Pycroft’s Petrel (P. pycrofti) – Identification confirmed on a couple of trips and seen at night around the Mokohinaus when the DOC-led team was staying out there (14-21 Jan). Possibly prospecting Mokohinaus as good numbers are seen at night there.
- Black-winged Petrel (P. nigripennis) – seen on a couple of pelagics and at the Mokes at dusk and through the night. I found several birds on the ground at Burgess but we couldn’t track down any burrows.
- Grey-faced Petrel (Pterodroma macroptera) – very much at the end of their breeding season and not seen on pelagics, although we did see adults flying at the Mokes at night, and found chicks all but ready to leave their nests. One young bird probably just fledged, flew onto our boat at night while anchored off Fanal Island. After a good feed of squid, courtesy of Mike (Imber), it was released again, with lights turned off!
- Black Petrel (Procellaria parkinsoni) – found north of LBI and towards the Mokes in reasonable numbers on all trips.
When we look at SST and Chlorophyll mapping through this period there has been a significant warming of the outer Gulf after 21 Jan and the start of a phytoplankton bloom at the end of the month. The last time such a bloom occurred (Nov 06) areas of the outer Gulf ‘emptied’ of seabirds, and this appeared to be happening again when I was last out (29 Jan).
Our seabird observation study for the Hauraki Gulf (begun in 2003) is ongoing, covers all seabirds and is supported for the most part by these pelagics (now over 100 trips). Participants include locals, overseas birders and overseas birding companies.
Happy seabirding
Chris Gaskin
Pterodroma Pelagics
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