Bermuda Petrel - Cahow

The Bermuda petrel (Pterodroma cahow) is a gadfly petrel. Commonly known in Bermuda as the cahow, a name derived from its eerie cries, this nocturnal ground-nesting seabird is the national bird of Bermuda, and a symbol of hope for nature conservation. For 330 years, it was thought to be extinct.

The dramatic rediscovery in 1951 of eighteen nesting pairs made this a "Lazarus species", that is, a species found to be alive after having been considered extinct. This has inspired a book and two documentary films. A national programme to preserve the bird and restore the species has helped increase its numbers, but scientists are still working to enlarge its nesting habitat on the restored Nonsuch Island.

Initially superabundant throughout the archipelago, the cahow is a slow breeder, but excellent flier. It spends its adult life on the open seas. At five years old, it returns to its former nesting place and begins breeding; the females lay one egg per season. Cahows mate for life.

The cahows' eerie nocturnal cries stopped the early Spanish seafarers settling the islands out of superstition, as they thought the isles were inhabited by devils. They put ashore hogs to breed as a living foodstore for passing ships. The boars interfered with the ground-nesting cahow and disrupted their breeding cycle.

Following Bermuda's colonisation by the English, introduced species like rats, cats and dogs, and mass killings of the birds by early colonists decimated the numbers of birds. Despite being protected by one of the world's earliest conservation decrees, the governor's proclamation "against the spoyle and havocke of the Cohowes," the birds were thought to have become extinct by the 1620s.

In 1951, 18 surviving nesting pairs were found on rocky islets in Castle Harbour by American ornithologist Robert Cushman Murphy and Bermudian naturalist Louis L. Mowbray. With them was a 15-year-old Bermudian boy, David B. Wingate. He devoted his life after that to saving the bird. After university studies and other work, in 1966 Wingate became Bermuda's first conservation officer.

Studying the birds and their habits, he set up a programme to build concrete burrows and wooden bafflers for the nesting tunnels, in order to keep out the slightly larger, competing Bermuda longtail. He worked to restore the habitat of nearby Nonsuch Island as a future viable base for the species.

Enjoying legal protection, the species has started to make a good recovery; the main threat for the future is lack of a suitable breeding habitat. Hurricane Fabian destroyed many nesting burrows in 2003. Researchers are repopulating the larger and ecologically-restored Nonsuch Island with chicks, their translocation timed so they will imprint on these surroundings and return here for nesting. This work is being undertaken by Bermuda Conservation Officer Jeremy Madeiros assisted by the Australian petrel specialist Nick Carlile. The global population of this bird in 2005 was about 250 individuals. A cahow was seen off the west coast of Ireland in May 2014, the furthest the species has ever been seen from Bermuda.