Cabbage Tree and Boondelbah Islands

Cabbage Tree and Boondelbah Islands Key Biodiversity Area

A seabird sanctuary of global significance

by Dan Vickers, BirdLife Southern NSW

Dan Vickers is on the Committee and Conservation Sub-Committee of Birdlife Australia Southern NSW Branch. Dan would like to thank Emily Mowat, the Guardian of this very special KBA, not only for her work as Guardian, but also for helping with this article.

Lying just 1.5 kilometres off the coast of Port Stephens, the small volcanic islands of Cabbage Tree and Boondelbah form one of Australia’s most important seabird breeding sites. Although covering only a few hectares, these rugged islands support internationally significant populations of breeding seabirds and provide a refuge for some of Australia’s rarest wildlife.

Recognised as a Key Biodiversity Area (KBA), Cabbage Tree and Boondelbah Islands are best known as the principal breeding stronghold for the endangered Australian subspecies of Gould’s Petrel (Pterodroma leucoptera leucoptera). Once perilously close to extinction, this remarkable seabird has become one of Australia’s greatest conservation success stories, thanks to decades of dedicated management and research.

Each year, Gould’s Petrels return to the islands after spending months foraging across the central Pacific Ocean. They raise a single chick annually before once again disappearing into the open ocean. On Cabbage Tree Island they nest in rock crevices between buttress roots and under fallen palm fronds beneath the island’s forest canopy. Over 90% of the Australia’s Gould’s Petrels breed on Cabbage Tree Island. A smaller population of around 50 pairs breeds on Boondelbah, mainly within artificial
nest boxes after a successful chick translocation program in 1999-2000 to create an insurance population. The species’ survival depends on the continued protection of these tiny islands.

Cabbage Tree Island nest box and Gould’s Petrels (photos Emily Mowat)

Boondelbah is also home to one of the largest breeding colonies of Wedge-tailed Shearwaters (Ardenna pacifica) on the New South Wales coast, and a smaller colony is present on Cabbage Tree Island. During spring and summer, thousands of shearwaters fill the islands with their distinctive calls as they return to their burrows after feeding far out at sea. Other breeding species include Little Penguins, White-faced Storm-Petrels, Short-tailed Shearwaters, Sooty Shearwaters, Sooty Oystercatchers and Great Cormorants.

Cabbage Tree Island is covered in lush subtropical rainforest dominated by the spectacular Cabbage Tree Palm (Livistona australis), whereas Boondelbah’s vegetation is dominated by low-growing Spiny-headed Mat-rush (Lomandra longifolia). Dense vegetation stabilises the fragile soils and provides nesting habitat for seabirds while protecting nests from erosion and extreme weather.

Despite their protected status, the islands face ongoing threats. Climate change is increasing the frequency of severe storms that can damage nesting habitat, while rising sea levels threaten low-lying coastal areas. Marine heatwaves can affect the distribution and availability of the fish and squid that Gould’s Petrels feed on at sea, which may affect their ability to successfully raise their chicks. Marine pollution, including plastics and discarded fishing gear, poses potential risks to seabirds feeding far from shore. Accidental introduction of predators remain one of the greatest dangers, making strict quarantine measures essential whenever researchers or managers visit the islands.

For this reason, public access to both islands is prohibited. They are managed as nature reserves by the NSW National Parks and Wildlife Service, allowing breeding birds to nest with minimal disturbance. Visitors can nevertheless enjoy excellent views of the islands and their surrounding waters from Port Stephens or during responsible wildlife cruises that operate under strict environmental guidelines.

Long-term monitoring by scientists and staff from NSW National Parks and Wildlife Service has documented the remarkable recovery of Gould’s Petrels following habitat restoration, the installation of artificial nest boxes on both islands, and the eradication of introduced rabbits from Cabbage Tree Island. These efforts have transformed the islands into a model for seabird conservation in Australia.

The Cabbage Tree and Boondelbah Islands KBA reminds us that even the smallest protected areas can play an outsized role in conserving biodiversity. These isolated islands are a sanctuary for seabirds, demonstrating the extraordinary conservation value of protecting breeding habitats from disturbance and invasive species.

BirdLife in action

BirdLife Southern NSW supports the conservation of this internationally significant Key Biodiversity Area by promoting awareness of its globally important seabird populations and advocating for the protection of Australia’s offshore island ecosystems. BirdLife Australia works with NSW National Parks and Wildlife Service, researchers and conservation partners to ensure islands such as these remain safe breeding refuges for threatened seabirds.

Our work includes:

Supporting seabird conservation through advocacy for the long-term protection and management of important breeding islands
Promoting science-based conservation, highlighting research that has contributed to the recovery of Gould’s Petrel and other threatened seabirds
Encouraging citizen science, with members recording pelagic seabirds and coastal observations through Birdata and participating in BirdLife Australia’s monitoring programs
Raising community awareness through talks, newsletters and educational activities that showcase the importance of offshore islands for Australia’s seabirds; and
Supporting marine conservation, recognising that healthy oceans are essential for the survival of breeding seabirds throughout their annual life cycle. Every observation submitted, every conservation action supported and every person inspired to value our seabirds contributes to the long-term protection of this remarkable island sanctuary.

Explore the KBA

Although the islands themselves are closed to protect sensitive breeding colonies, there are excellent opportunities to appreciate their wildlife from the surrounding coastline and waters.

Tomaree Head summit walk

Distance: 2.2 km return (moderate)
One of New South Wales’ most spectacular coastal walks, the summit provides sweeping views across Port Stephens, Cabbage Tree Island, Boondelbah Island and the offshore islands. During the breeding season, seabirds can often be seen soaring offshore, while migrating Humpback Whales are common from May to November.

Fingal Bay and Barry Park lookouts

These coastal vantage points offer excellent views towards the islands and opportunities to observe seabirds, dolphins and passing whales. Early mornings often provide the best viewing conditions.

Port Stephens wildlife cruises

Several licensed eco-tour operators offer cruises around the islands, providing excellent opportunities to observe seabirds, dolphins and other marine life without disturbing nesting colonies. These cruises remain outside protected landing areas while offering close views of the islands.

Boat Harbour and Birubi Point

These coastal headlands provide good opportunities to observe shearwaters, gannets, terns and skuas during seasonal seabird movements, particularly after strong onshore winds.

Birding tips

● Bring binoculars or a spotting scope for the best views from the mainland
● Spring and summer are the peak breeding seasons for Gould’s Petrels and Wedge-tailed Shearwaters
● Winter and spring are excellent times to combine seabird watching with whale watching; and
● Respect exclusion zones around the islands and avoid disturbing seabirds from boats.

Key species

Gould’s Petrel
Wedge-tailed Shearwater
White-faced Storm-Petrel
Little Penguin
Sooty Oystercatcher
White-bellied Sea-Eagle
Crested Tern
Australian Pied Oystercatcher