2018: A bad year for takoketai and a grim forecast

(Environmental News #40)

KATE WATERHOUSE summarises recent data from Wildlife Management International’s researchers Nikki MacArthur and Elizabeth (Biz) Bell.

Warming sea surface temperatures associated with climate change could represent a new, emerging threat to takoketai/black petrel. In combination with ongoing fisheries‐related mortality at sea, and predator impacts on land, this threat could increase the rate of black petrel population decline over the next 5 to 10 years. Since Biz Bell made her first trip up ‘the hill’ (as she calls Hirakimata/Mount Hobson), many things have changed. Bell knows now that the black petrel is called takoketai (Procellaria parkinsoni) and that taiko is a name southern people used for their local species, the Westland black petrel (Procellaria westlandica). Bell has also been instrumental in visits by fishermen up the hill to see first‐hand one of New Zealand’s greatest travelers.

...only 10% of birds that leave Aotea|Great Barrier Island return to breed successfully.

In a land built on the efforts of great ocean navigators, black petrel can take pride of place. Bell has attached tiny GPS trackers to fledgling birds to try to confirm the extent of their travels, and to begin to understand why only 10% of birds that leave Aotea|Great Barrier Island return to breed successfully. This information is the key to black petrel survival into the next century.

Lighter and smaller birds

Birds now are lighter and smaller than they were when Bell first began studying them on Hirakimata in 1995. This trend is common amongst seabird species in the Hauraki Gulf and on islands off the northeast coast of the North Island. Bell and other seabird scientists put this down to lower food availability, due to overfishing of squid, krill and small fish in the Pacific Ocean.

Climate change is complicating the picture, warming inshore sea temperature, and pushing krill out of waters near the breeding colony on Hirakimata meaning birds feeding chicks or incubating eggs must fly further to feed.  On average, female black petrels tracked last season flew 4,273 km on foraging trips during breeding.

None of these factors alone are necessarily catastrophic, but together they could constitute a slow and inexorable path to extinction for black petrel, and many of New Zealand’s other burrowing seabirds. The ongoing decline in seabird populations continue to have a significant impact on other parts of the ecosystem. New Zealand’s forests evolved with seabirds burrowing beneath their roots and depositing nutrient‐rich guano into the soil (1,2).

Seabird colonies may even have regional or global effects on the cycling of elements such as nitrogen and phosphorous, far beyond the colony (3). The positive flow‐on effect of these nutrients is now lost to most New Zealand mainland forests, where seabirds no longer breed. On Aotea, the decline continues, with Cook’s and black petrel burrows along the ridges of Coopers Castle, and Te Paparahi in the north, destroyed by pigs in the last decade.

The effect of La Niña on breeding success

Only 52% of study area burrows were occupied by breeding pairs during the 2017/18 season, the lowest occupancy rate recorded since 1999 and 9% lower than the 19‐year average of 61%. The fledging success (62%) was also the second lowest recorded since 1995 and 11% lower than the 23‐year average of 73%.

This lower than average breeding success appeared to be driven by climatic factors consistent with La Niña conditions. These include more frequent warm northerly and northeasterly winds than normal, heavy rainfall associated with three ex‐tropical cyclones in February, and above average sea‐surface temperatures in northern New Zealand waters (4).

Among the 278 breeding burrows, 105 breeding failures were recorded, a failure rate of 38%. Causes of failure included eggs or chicks being washed out of, or drowned, in burrows, eggs or chicks disappearing from burrows, eggs being abandoned or crushed, and chicks dying from starvation.

Sea temperatures changing food availability

The anomalous sea‐surface temperatures observed in the summer of 2017/18, may have altered the distribution and accessibility of black petrel prey, reducing the foraging efficiency of some birds. Some climate models are now forecasting a prolonged period of unusually high global sea‐surface temperatures between 2018 and 2022 (5). Higher than average summer and autumn sea surface temperatures for the Tasman Sea and southwest Pacific could result in a series of relatively poor breeding years for black petrel. Tracking by GPS of breeding adults undertaking chick‐provisioning trips during March and April 2018 (Figure 1) found that adults were travelling an average of 3,633 km (6).

Tracking devices were deployed on 40 adult birds during chick rearing, yielding 32 complete chick‐feeding tracks. These tracks showed that foraging black petrel were travelling substantially longer distances during the 2017/18 breeding season than had been reported previously. These longer distances indicate that warmer than average sea‐surface temperatures may have reduced the birds’ foraging efficiency.

...foraging black petrel were travelling substantially longer distances ... than had been reported previously.

In comparison, nine breeding adults tracked in February and March 2006 (the first time black petrel were successfully tracked) travelled an average distance of 806 km. The birds spent a significant period foraging near the continental shelf off the northeast coast of the northern North Island (7).

Adult black petrel continue to use previously identified foraging hotspots at the continental shelf break, and over the eastern Chatham Rise. New foraging hotspots were also detected in coastal waters off the west coast of Northland, along the Norfolk and Kermadec ridges, and in pelagic waters to the north and east of the Chatham Rise (see Figure 1).

Geolocator devices have been deployed on adult birds migrating to wintering grounds in the eastern Pacific. Tracking data (Figure 2) shows that these birds spent a lot of time within a relatively small area of the eastern Pacific, off the coast of Ecuador and around the Galapagos Islands (8).

Unsustainable fisheries bycatch

Black petrel is recognised as the seabird species at the greatest risk from unsustainably high rates of bycatch in commercial fisheries both within, and beyond, New Zealand’s Exclusive Economic Zone (9). To adequately manage this threat, a spatially‐explicit model of bycatch risk is required, incorporating measures of fishing effort, methods and black petrel at‐sea distribution and habitat use (10).

Estimates of the at‐sea distribution have to date been generated using a combination of remote tracking data and at‐sea counts carried out by fisheries observers and recreational birdwatchers. This data does not adequately describe the at‐sea distribution of takoketai at all life stages, nor does it adequately describe variation in at‐sea distribution in response to changes in sea surface temperatures and other environmental variables (10).

Lifting our game: ensuring breeding birds and chicks are protected in NZ waters

Bell and her team are winding up the 2018/19 breeding season monitoring as Environment News goes to print. Only around 1‐in‐10 black petrel they banded this season will make it back to Aotea to breed. While the species is long‐lived (up to 30 years), the ongoing population decline and low rate of survival to breeding age means protection of the birds is critical when they are in New Zealand waters and at the main colony on Hirakimata. Like many other species of seabirds breeding in northern New Zealand, black petrel now face an additional and increasing threat from climate change. Smaller breeding birds, undertaking longer foraging trips, will have lower breeding success. Ultimately, this effect is likely to have a negative flow‐on to an already low juvenile survival rate.

Ensuring the survival of black petrel

Despite the bleak predictions, some very  concrete actions can be taken to fully protect  black petrel when they are in New Zealand  waters and at their breeding colonies. These  include: 

·         Feral cat control on and around Hirakimata: The Department of Conservation has  established regular cat trapping around the  colony. Cats are opportunistic and thought  to move up the mountain in search of food.  Hunting cats out of the area and  surrounding ridges is an option not yet  taken up. 

·         Pig control on and around Hirakimata: Pigs  have been observed destroying burrows and  presumably predating eggs and chicks,  leading to loss of satellite colonies  elsewhere on the island (including on  Tataweka and Coopers Castle11. 

·         Reduce or eliminate at sea seabird risk through mitigation by commercial fishers:  Risks of black petrel being caught in surface  and bottom longline and trawl fisheries is  well understood. Significant efforts have  been made to educate and motivate the  inshore fleet, in particular through the Black  Petrel Action Group. Fishers signing up to  this group in 2014 committed to using  mandatory mitigation and best practice to  avoid killing birds when setting long lines  and hauling in (birds dive on the baited  hooks and unused baits and are either  drowned or caught in the hauler).  Monitoring outcomes and the activities of  the fleet is very limited, an unsatisfactory  situation for the largest known preventable  cause of death for breeding black petrel. 

·         Understand and reduce the at‐sea risk to juvenile birds in the eastern Pacific. The area  still in most need of attention. Current  research by Wildlife Management  International is expected to shed more light  on the movement of birds in the eastern  Pacific Ocean. Inter‐governmental action is  required. 

Multiple pressures and known solutions – it’s time to act

Warming sea‐surface temperatures associated  with climate change represent a new, emerging  threat to New Zealand’s most at‐risk seabird.  With ongoing (and largely avoidable) impacts  on land and at sea continuing, population  decline over the next 5 to 10 years will worsen.  The Department of Conservation and Ministry  of Primary Industries are jointly responsible for  the protection of black petrel in New Zealand.  It is certainly time for these agencies to step up  and act.

Takoketai ‐ Nationally Vulnerable—Black Petrel

Takoketai/black petrel is ranked as Nationally Vulnerable under the New Zealand Threat Classification System and Vulnerable on the IUCN Red List of Threatened Species. They are the seabird species at greatest risk of being adversely impacted by unsustainably high rates bycatch in commercial fisheries within New Zealand’s Exclusive Economic Zone (12). Bottom‐longline fisheries are the key risk to black petrels, but birds also die in surface longline and trawl fisheries. Takoketai/black petrel are also exposed to threats on land, principally predation by feral cats, ship rats and pigs (13). A long–term research project aimed at quantifying these population parameters was initiated in 1995/96 (13). A network of study burrows has been established within a 35‐ha study area near the summit of Hirakimata/Mt Hobson on Aotea|Great Barrier Island. During the 2017/18 season, 450 study burrows were monitored.

Notes:

1 Doughty, C. E., Roman, J., Faurby, S., Wolf, A., Haque, A., Bakker, E. S., Svenning, J. C. 2016. Global nutrient transport in a world of giants. Proceedings of the National Academy of Sciences, 113(4), 868–873.

2 Perry, G. 2018. Ecological function in an age of extinction. Environment News, Issue 39, Winter 2018. Great Barrier Island Environmental Trust.

3 Otero, X.L., Peña‐Lastra, S., Pérez‐Alberti, A., Ferreira, T.O., Huerta‐Diaz, M.A. 2018. Seabird colonies as important global drivers in the nitrogen and phosphorus cycles. Nature Communications 9, Article number: 246 (2018).

4 NIWA. 2018. New Zealand Climate Summary: Summer 2017‐18. Issued March 2018. NIWA National Climate Centre.

5 Sévellec, F., DrijĬout, S.S. 2018. A novel probabilistic forecast system predicting anomalously warm 2018‐ 2022 reinforcing the long‐term global warming trend Nature Communications 9, Article number: 3024.

6 McArthur, N., Ray, S., Crowe, P., Butler, D., Bell, M., Bell, E. 2018. Population trends, breeding distribution and habitat use of black petrels (Procellaria parkinsoni) – 2017/2018 operational report.

7 Freeman, R., Dennis, T., Landers, T., Thompson, D., Bell, E., Walker, M., et al., 2010. Black Petrels (Procellaria parkinsoni) Patrol the Ocean Shelf‐Break: GPS Tracking of a Vulnerable Procellariiform Seabird. PLoS ONE 5(2): e9236. https://doi.org/10.1371/journal.pone.0009236.

8 Bell, E.A., Sim, J.L., Scofield, P. 2011. At‐sea distribution and population dynamics of the black petrel (Procellaria parkinsoni), 2007/08. DOC Marine Conservation Services Series 8. Department of Conservation, Wellington. 37p.

9 Richard, Y., Abraham, E.R. 2013. Risk of commercial fisheries to New Zealand seabird populations. New Zealand Aquatic Environment and Biodiversity Report No. 109. March 2013. Ministry for Primary Industries.

10 Richard, Y., Abraham, E.R., Berkenbusch, K. 2017. Assessment of the risk of commercial fisheries to New Zealand seabirds, 2006–07 to 2014–15. New Zealand Aquatic Environment and Biodiversity Report 191.

11 Bell, E. 2018. Pers. comm.

12 Abraham E. R., Richard, Y., Bell, E., Landers, T. J., 2015. Overlap of the distribution of black petrel (Procellaria parkinsoni) with New Zealand trawl and longline fisheries. New Zealand Aquatic Environment and Biodiversity Report 161. October 2015. Ministry for Primary Industries.

13 Whitehead, E.A., Adams, N., Baird, K.A., Bell, E.A., Borrelle, S.B., Dunphy, B.J., Gaskin, C.P., Landers, T.J., Rayner, M.J., Russell, J.C. 2019. Threats to Seabirds of Northern Aotearoa New Zealand. Northern New Zealand Seabird Charitable Trust, Auckland, New Zealand. 76pp.