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Broad-Billed Prions/Parara (Pachyptila vittata) – Storm Wreck

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Pre- and Post-wash prions
Photo credit: Wildbase, Massey University

In July 2011 the North Island experienced one of the largest storm wrecks of prions ever recorded.

This ‘wreck’ phenomenon was caused by six days of continuous southerly winds and storm fronts which precluded these small pelagic seabirds from feeding at sea or resting on the sea surface.  Estimates of total mortality were made based on beach counts and range widely (25,000 - 300,000 individuals). There were many similarities between this storm wreck and what we face during a large oil spill event.

Broad-billed prions are the largest of the prions and are found throughout the oceans of the southern hemisphere.

The global population of broad-billed prions is estimated at over 15 million by Brooke (2004) and the IUCN affords them a low conservation status (Least Concern; IUCN 2011). However, the species is locally deemed to be ‘at risk’ as a ‘relict population’ – meaning that evidence suggests their original breeding range has decreased by more than 90% following the introduction of predatory mammals to New Zealand (Miskelly 2008).

Broad-billed prions breed on many islands around southern New Zealand, where historically they were harvested for food by Maori (Heather & Robertson 1996). They are now a fully-protected native species. This species feeds at the sea surface on small copepods, crustacea and plankton using the sieve like lamellae of the upper bill. Storm-wrecks of this species are common on New Zealand’s west coast beaches between June and January each year.

The response

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One of the petrels being released at sea.
Photo credit: Thomas Burns

Over the first seven days of the response Massey admitted 613 prions, 97% of which were broad-billed prions with the other three percent being a mix of Salvin’s prions, Antarctic prions, fairy prions, slender-billed prions, and one diving petrel. On admission the birds were immediately given oral fluids to combat dehydration and were then started on a twice-daily feeding regime where fluids were given at feeding time too. Thermoregulatory assistance was provided throughout the process with birds being kept in warmed rooms with individuals being placed in incubators as required. Birds in care were also provided with antifungal medications as a preventative measure against aspergillosis, a fungal disease which is common to seabirds during hospitalisation.

This is very similar to an oil spill response, with the only addition being that on admission, birds would also have their eyes, nares (nostrils) and mouth cleared of oil.

Once birds had regained body condition and strength, attention turned to preparing the birds for release by assessing feather health, in particular, the waterproofing abilities of feathers. To do this, birds were placed in rehabilitation pools and encouraged to swim and preen. We learnt a lot during this period – and called on advice from International Bird Rescue (IBR) when it became apparent that waterproofing abilities were generally decreasing through time instead of improving. With the help of IBR it was decided that: 1) birds should be washed ; 2) the oil content in the birds diet should be reduced, and; 3) the flow rate into the rehab pools should be increased in an attempt to improve water quality. Thankfully this strategy worked well, with all birds ready for release in only a matter of days following their wash!

Unfortunately, and because many birds were severely compromised on admission, only 21% of birds survived to be released, with the remainder dying in care or being euthanased. Despite this being a less than ideal outcome, over the duration of the response we learned a great deal about the complexities of dealing with large numbers of seabirds and the resources required to sustain a large response.

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