Population Status Trends
Bermuda Petrels once bred abundantly throughout Bermuda. After 1621, the bird was considered extinct for about three centuries, until their continued existence was confirmed in the early 1900s. In 1951, 18 pairs were rediscovered breeding on Castle Harbor. Forty-five years of intensive management has resulted in slow but steady increases in population of this species, but total numbers remain extremely small. Breeding success has increased from 5 percent per year in the 1950s to more than 25 percent per year in the 1990s, with 70 pairs fledging a record 40 young in 2003, and 71 pairs fledging 35 young in 2005. BBS and CBC data are not available for this species. The Bermuda Petrel is federally listed as an Endangered Species.
The Cahows' eerie nocturnal cries deterred superstitious early Spanish explorers from settling on Bermuda. But the bird was nearly exterminated in the 1600s by British colonists who hunted it for food, destroyed its breeding habitat, and introduced predators, including rats, dogs, and cats. Bermuda Petrels were considered extinct for about 300 years.
Following the birds' rediscovery in 1951, the Bermuda Conservation Programme periodically removed rats, installed concrete nesting burrows with wooden baffles over burrow entrances to keep out larger, competing White-tailed Tropicbirds, and ecologically restored a larger nearby island—Nonsuch Island—as a potential nesting site. The Castle Harbor islands were made a national park.
Under legal protection and intensive management, the species is slowly recovering. However, nearby light pollution hampers the birds' nocturnal courtship. In addition, contaminants may contribute to increased egg failure. But the primary threat is limited breeding habitat. Increasing sea levels and storm activity flooded nesting sites in the 1990s, and Hurricane Fabian washed over the breeding islets in 2003, destroying many nesting burrows.
In 2004, with a new artificial burrow complex built on a higher section of one islet, a sound attraction system pioneered by Audubon's Seabird Restoration Program was set up, and adult Cahows moved there from the destroyed sites. Three pairs occupied burrows in the new site by the spring of 2005. Beginning in 2004, a few Bermuda Petrel chicks were translocated to Nonsuch Island, fed, and monitored, in the hopes that they would imprint on these surroundings and return when mature to nest. All translocated chicks fledged successfully. This project is scheduled to continue for three more years, with plans to translocate a total of about 100 chicks.