What happens to fledgling Black Petrels at sea?

Biz Bell bands a Black Petrel on Great Barrier Island

The ACAP-listed and globally Vulnerable Black Petrel Procellaria parkinsoni is a New Zealand endemic that breeds on Great and Little Barrier Islands at the edge of North Island’s Hauraki Gulf.  The breeding colony on the upper slopes of Mount Hobson/Hirakimata on the former island has been studied for many years by the New Zealand-based ecological consultancy Wildlife Management International, with burrows marked and monitored every breeding season.  Adults and chicks close to fledging are banded for identification but fewer fledglings than might be expected have been returning to the study colony to prospect for burrows as young adults and commence breeding.

An illustrated article recently published online by RZN News describes the 29-year study and considers what might be happening to the birds in their first few years at sea.  The article states “… on average, more than 70 percent of petrel parents monitored by the survey successfully fledge a chick each year.  But of the thousands of chicks that have been banded over the decades, only about 10 percent of them have ever been found again.  What happens to the rest is still largely a mystery”.

Black Petrel at sea off North Cape, New Zealand, photograph by Kirk Zufelt

In the article, the Managing Director of Wildlife Management International Elizabeth ‘Biz’ Bell is quoted as saying "We've banded over 5500 chicks over the 29 years and we've had less than 500 return.  Is that because we can't search this entire, massive island and they're somewhere else?  Are they dying at sea?  Are they dying on migration?  Are they dying in fishing boats? Are they dying from pollution events, climate change?  It's one of our biggest gaps of knowledge.”

Black Petrels are known to be caught on long lines.  Adoption and implementation of ACAP-approved best-practice mitigation measures by fisheries throughout the species’ at-sea range is required to reduce the numbers of fledglings assumed to being drowned on hooks.

With thanks to Susan Waugh for information.

John Cooper, Emeritus Information Officer, Agreement on the Conservation of Albatrosses and Petrels, 26 February 2025