By Rex Graham
When seabirds die in large numbers, the phone of ornithologist Dr. Colin Miskelly rings. He answered a call on July 12 that had mind-boggling implications. A Department of Conservation colleague reported that Broad-billed Prions, which spend their lives at sea, had been blown over the Tararua Range of New Zealand’s North Island.
And then reports of massive prion fatalities on New Zealand’s western coast began arriving.
Since 1986, hundreds of volunteers patrolling about 3,700 km of New Zealand coastline have documented up to 14,462 dead petrels, shearwaters, penguins and other seabirds in single “wrecks” due to sudden disappearance of food or bad weather. But Miskelly, Curator of Terrestrial Vertebrates at Te Papa Museum of New Zealand, suspected the July wreck may reach 350,000 birds.
“The true scale of the event was massive,” said Dr. Phil Battley, senior lecturer in zoology at Massey University, Palmerston North, New Zealand, at the time. “People found 400 to 500 birds per km most places they look along the North Island, and that’s just the ones on the surface that were not covered by sand.”
Battley suspects that at least 100,000 birds died, mostly Broad-billed Prions (pronounced PRY-ons). “But how many more died is an open question,” he said.
As anecdotal reports and careful counts are compiled and ornithologists analyze the increasingly gruesome statistics, the estimated death toll rises.
“Far more prions were killed in July than during the total history of seabird wrecks recorded over 37 years by the Ornithological Society of New Zealand’s Beach Patrol Scheme,” said Miskelly. “Details are still being collected and collated, but large numbers have been found between Dargaville to Okarito, which are 900 km apart. In places, over 400 birds were stranded per kilometre of coast, and more were blown inland.”
Small numbers of other species of storm-pummelled birds also were found dead. Survivors included Salvin’s Prion (Pachyptila salvini), Antarctic Prion (Pachyptila desolata), and Slender-billed Prion (Pachyptila belcheri).
Miskelly, Battley and other scientists agreed that roughly 90% of all dead and exhausted birds were Broad-billed Prions (Pachyptila vittata). “The largest previous wreck of Broad-billed Prions was about 1,400 birds,” said Miskelly. “But the 2011 wreck is likely to be 250 times larger.”
Blown in the winds
Beginning about July 6 and continuing for a week, relentless winds blew north from Antarctica toward Australia then bent east toward New Zealand, eventually sweeping Broad-billed Prions (Pachyptila vittata) toward New Zealand’s west coast. Thousands of the gray seabirds with a wingspan up to 66 centimetres, weighing about 200 grams were grounded in what Miskelly, Battley and other New Zealand scientists consider to be the largest avian wreck on record for any bird species in New Zealand.
Bird rescue centres swamped
Concerned residents rescued dozens, and then hundreds of exhausted and cold prions. People carried dozens of birds in boxes, dog crates or other containers to Massey University’s Wildlife Health Centre, or local vets and bird rescue centres. The unprecedented numbers of birds being handed in alive signalled that the wreck was huge. “The Massey vets had received 270 prions by July 12, but Kapiti SPCA (in Waikanae, NZ) received more than 500, including 400 in one day,” Battley said.
About 200 Broad-billed Prions were taken to the Anexa Raglan Vet Clinic in Raglan, NZ. “Keeping these birds alive has been such a challenge. Department of Conservation people and other birders told us that they would probably all die but we were hoping to prove them wrong,” said Moana Robb, junior veterinary nurse at the Raglan clinic. “It’s been really disheartening and quite gutting that we are down to our last two out of about 200.”
Media reports included accounts of hundreds of birds found dead on beaches, or simply sitting on land, still alive but unable to fly out to sea to eat.
Pukerua Bay resident Jaroslav Benc told The Dominion Post that he saw dead birds littering the beach.
Jared Smith, a writer with the Taranaki Daily News, said New Plymouth’s Department of Conservation offices looked like “a casualty ward for seabirds as a steady stream of victims poured in this week.”
“By 9 p.m. tonight (July 14) when we went home, we had admitted 549 prions,” said Dr. Brett Gartrell, director of the New Zealand Wildlife Health Centre at Massey University.”The birds are coming in with starvation, anaemia, hypothermia and dehydration. About 100 of these died in care. Another 100 were dead on arrival. Wellington Zoo has over 600, Hamilton rehabilitators have about 100.”
The first release of the strongest rescued prions from Massey University began on July 15.
Life and death on the winds
“Prions are a group of six small, closely-related seabirds that are hugely abundant in southern oceans,” Miskelly said. “They are petrels, and like most petrels, typically breed in enormous colonies on remote islands free of introduced predators.”
Like all petrels, prions live at sea, coming to land only so that females of nesting pairs can lay a single egg in a burrow nest and feed their young.
The three prion species with the widest bills, including the Broad-billed, use comb-like structures along the edge of the upper mandible to filter tiny crustaceans and other small animals and their eggs from seawater. Prions seek out the food bounty of ocean upwellings.
Miskelly, an expert on prion behavior, said prions are usually unfazed by strong winds, and actually use them to fly long distances with ease. But for more than a week in July, gale-force winds continually pushed locally breeding prions eastward toward danger: land.
Reports by MetService, an international weather forecasting service, said fast-moving showers and thunderstorms pummelled New Zealand on July 9, with damaging winds on the Kapiti Coast blowing 70 to 90 km per hour. A tornado reported by eye witnesses was associated with a strong thunderstorm east of Waikanae at 4 p.m. on July 9.
As New Zealand’s western shore loomed closer, prions began to struggle to avoid it. Eventually, they were driven ashore in exhausted waves in the tens of thousands, possibly hundreds of thousands.