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In the 1600s, animals brought by settlers left Bermuda’s cahow almost extinct; rediscovered in 1951 with only 18 pairs, it now has 165 breeding pairs
Bermuda’s cahow was thought extinct for 300 years until 18 pairs turned up in 1951. Decades of rescue work have raised the count to 165 breeding pairs.
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Some species get a second chance. The cahow is one of them. This seabird was thought extinct for over 300 years. It now has 165 established breeding pairs, according to Jeremy Madeiros, Bermuda's chief terrestrial conservation officer, writing on the Nonsuch Expeditions site. In 2025, 78 chicks successfully fledged, the second-highest total on record, behind only the 79 chicks of 2021.
How settlers nearly wiped out the cahow
The cahow, or Bermuda petrel, breeds exclusively in Bermuda. Long ago, it was found across the islands. Then the settlers arrived. Madeiros wrote that settlers introduced hogs, cats, and dogs, while rats arrived by accident. Together, these animals quickly decimated the bird, and by the 1620s the cahow was considered extinct.
Hunting was painful too. A 2012 study in Bird Conservation International by Nicholas Carlile, David Priddel and Jeremy Madeiros says Nonsuch Island was believed to be one of the “bird islands” where early settlers collected hundreds of birds each night for food. The authors think the birds there probably declined due to overharvesting, and then disappeared when the land was cleared and overgrazed.
A surprise rediscovery and years of rescue work
Deep Dive
The bird’s last nesting sites remained undiscovered for about 330 years. Then, in 1951, only 18 breeding pairs were rediscovered on four tiny half-acre rocky islets, Madeiros says. The study reports slightly different early figures: 13 to 14 pairs on three islets in 1951, and a 1961 survey that found two more breeding sites, raising the known total to 18 pairs.
Dr. David Wingate managed the species for 40 years. He controlled the rats and built artificial burrows; when he retired in 2000, the population had risen to 53 pairs. Madeiros has managed the work for the past 25 years, he wrote in July 2025, and the population has since tripled to 165 established breeding pairs.
Moving chicks to a safer island
The original islets are small and low-lying, under 10 meters (about 33 feet) high, and vulnerable to storm damage, the study says. It identified storm damage and erosion as the biggest threat to the bird’s survival at the time. So the team turned to larger, nearby Nonsuch Island, which is higher and far more resistant to hurricane flooding and sea level rise.
Between 2004 and 2008, the team moved 104 near-grown chicks there and hand-fed them fish and squid. All but three fledged successfully. The first egg on Nonsuch in more than 300 years was laid in January 2009. Madeiros says two five-year projects moved 175 chicks in all, so the birds could imprint on their new home before heading out to sea. Almost half of them returned as adults three to six years after fledging, and the first returned birds produced the first naturally hatched chicks on Nonsuch since the 1620s.
A comeback that is still unfinished
Since that first egg in 2009, the Nonsuch colonies have grown to 40 breeding pairs. Madeiros says the island could eventually support up to 5,000 pairs, but he does not expect to live to see those numbers. He still considers the cahow endangered, and the 2012 study called it one of the rarest seabirds in the world. In a March 2026 update, he reported that eight chicks had hatched in one Nonsuch colony, with ten more eggs on the way: five hatching and five fertile eggs still developing. The cahow’s story shows what patient conservation can achieve.
