Islands Where Removing Invasive Predators Brought Seabirds Back

Ten years after black rats were removed, the restoration trustees reported four times as many Scripps's murrelet nests. They also recorded ashy storm petrels nesting on the island. The murrelet in the photo is on a nest in a sea cave, one of the places the survey team had to check.

Tufted puffins were recorded nesting here in 2013, the first such record on Hawadax. After Norway rats were removed, researchers also documented black oystercatchers and glaucous-winged gulls producing chicks. The two observations tell different parts of the recovery story. One establishes a new nesting record. The other shows that birds already present were raising young.

The 2001 survey estimated 297 pairs of Manx shearwaters. By the 2023 census the observatory reported about 25,000 individuals, a different unit that still gives you a feel for the scale of the recovery. Lundy was declared rat-free in 2006, and European storm petrels were first confirmed breeding in 2014.

Gray petrels were recorded back on Macquarie in 1999 as feral cat control progressed. Their comeback continued after rats, mice, and rabbits were removed. The Australian Antarctic Program links part of that improvement to tussock growing back after rabbit grazing ended. Finding a bird back on the island was the beginning of the story.

After feral cats were removed, researchers recorded five seabird species recolonizing the main island in small numbers. Sooty terns, which had kept nesting there, also benefited. Researchers found far fewer dead adult terns at their colonies after the cats were gone. The photo shows sooty terns at Mars Bay.

Early signs came from King Edward Cove. After rats were removed from its shores, researchers went from seeing Wilson's storm petrels in the low tens to routinely seeing hundreds five years later. Those observations show more birds using the area, while a nest count would answer a different question.

Residents helped restore two inhabited islands for breeding seabirds. After rat removal began in 2013, Manx shearwater chicks fledged on St Agnes and Gugh for the first time in living memory. Checks by the community continued after the islands were declared rat-free in 2015.

Manx shearwaters nest in burrows, so a steep grassy slope can hide a breeding colony. On Ramsey the RSPB recorded the shearwaters recovering after brown rats were removed. This is an island to compare with Lundy if you want to see how the same bird benefited from similar work in two different places.

Black-winged petrels were already nesting here, but relatively few attempts succeeded. The island board reported an increase in breeding success from 2.5% to more than 50% following rodent removal. It's a reminder that the most important change at a colony can happen inside burrows you're already looking at.

After rats were removed in 2011, conservationists later used seabird calls and decoys to draw birds back. A gray-backed tern chick was one of the first encouraging signs. Palmyra shows why a safe island can still need help bringing birds back to breed.

A burrow camera recorded a Bulwer's petrel chick emerging and fledging after rat removal work. It was the first time the field team had caught that outcome on camera. Hawaiʻi declared Lehua rat-free in 2021, and later monitoring reported improved reproductive success among native seabirds nesting on the islet.

Project partners reported 892 Yelkouan shearwater fledglings in 2017 while rats were still present and estimated about 7,800 in 2019 after their removal. Those figures count young birds rather than breeding adults, which gives a clearer picture of how many chicks were making it out of the nest.