Once widespread and abundant on the Chatham Islands, the Chatham petrel was until recently restricted to Rangatira Island where competition for burrows with other seabirds saw the population dwindling.
Active management has allowed the population to grow and new populations on Pitt and Chatham Islands are being created.
Chatham petrel. Photo: Don Merton.
John Adams checking the band on a Chatham Petrel
The Chatham petrel is a medium-sized grey, white and black petrel with a distinctive dark 'M' pattern across the spread upper-wings. They have a wingspan of up to 70 cm and weigh around 200 g.
Finds of subfossil Chatham petrel bones from around the Chatham Islands indicate that Chatham petrels were once widespread on the islands and were one of the more abundant burrowing seabirds. By 1900 the breeding range of the Chatham petrel was confined to forested areas on 241 ha Rangatira Island and until recently this remained the sole breeding site.
The population is estimated to be about 1,000 birds with 100-130 breeding pairs being actively managed since 1999 in an effort to increase productivity.
A single white egg is laid in December and chicks fledge in May–June.
During the breeding season Chatham petrels feed up to 3,000 km south-east of the Chatham Islands. They over-winter off the coasts of Peru and Chile.
Broad-billed prion compete with Chatham petrel
The loss of forest habitat on Chatham and Pitt islands, along with the introduction of mammalian predators such as cats, rats and pigs lead to Chatham petrels being confined to predator-free Rangatira Island by around 1900.
Farming ceased on Rangatira in the early 1950's and despite considerable recovery of the forest, it was found that Chatham petrel numbers were declining, with only 30 breeding pairs known in the 1980's.
It was discovered that competition from broad-billed prions was causing most Chatham petrel breeding efforts to fail and efforts have been made to protect burrows and chicks from prion interference. Hundreds of thousands of broad-billed prions breed on Rangatira.
Dan Palmer fitting a flap to a Chatham petrel burrow entrance
A key part of DOC's work on Rangatira island is to ensure that no unwanted pests, like rats or mice, arrive on the island where they might have a serious impact on Chatham petrel and other vulnerable birds.
DOC staff make several trips to Rangatira Island every year to manage Chatham petrel burrows to maximise chick productivity. Artificial burrows are installed for known breeding pairs and these are blocked off over winter when the petrels are away to ensure that broad-billed prions do not take over the burrow in their absence.
Neoprene flaps, designed by Lincoln University, are fitted over the burrow entrances and these allow the petrels through but deter most prions from entering. Staff also make regular inspections of the nests during periods of peak prion activity.
Chicks, collected late in the breeding season, have been translocated to predator-fenced sites on Pitt and Chatham Islands where they have been fed until their departure to sea. This, along with a sound system playing petrel calls has has been successful in establishing small breeding colonies on Pitt and Chatham Islands.
You can help
Feeding a translocated Chatham petrel chick
If you are travelling to the Chatham Islands, or transporting goods or livestock there, be careful that you don't inadvertantly introduce pest animals or plants or diseases. They could threaten Chatham petrel or other rare and endangered flora and fauna in this unique environment.
Your sponsorship can also help the department with the conservation management techniques used to protect Chatham petrel, including:
- Radio telemetry, used to catch and track adult birds and follow them to their burrows. This helps to increase the number of burrows under management.
- Predator fencing to create new sites for Chatham petrel colonies.
- Translocation and feeding of chicks at new sites.