Hurricanes and Bermuda Petrels
Hurricane Florence Threatens the Island Nesting Burrows of the Bermuda Petrel - the Only Breeding Site for this Endangered Bird.
Bermuda Petrels (Cahows), nest on offshore islands in Bermuda. Hurricanes wash away sections of these islands and threaten the breeding season of the endangered birds.
Hurricane Florence passed just to the west of Bermuda on Monday, September 11, 2006 - indications were that the storm would be a Category 2 hurricane by that time but, mercifully, it remained a Category 1. Bermudians were not only worried about their homes and properties: many of them were also thinking of the Bermuda Petrel (Pterodroma cahow), their national bird.
The Bermuda Petrel, or Cahow, was believed extinct for some 300 years until 1951, when a small breeding colony was discovered on offshore islands in Bermuda. Formerly an inhabitant of the larger islands, where it likely nested in forest burrows, the bird was virtually wiped out by the arrival of humans and other introduced species. Remnants of the population survived offshore where they were safer from predators and other threats, but much more exposed to the elements. In 1951, there were only seven breeding pairs left.
The petrels had survived in decreasing numbers, unnoticed by the human inhabitants of Bermuda because they were so few, and because they are present for only part of the year and fly by night. Efforts to save the species began but the population increased very slowly - only a handful of young were raised each year, and fledglings don't return to breed for several years. The Bermuda Department of Conservation (BDC) helped the species recovery by providing artificial nesting burrows made from concrete.
The petrels return to the same burrow year after year and this is a problem for the small breeding colony: the existing petrel burrows on four tiny islands are threatened by the powerful tropical storms and hurricanes that track past Bermuda each hurricane season - the burrows are too low and the islands are subject to severe storm damage from powerful waves.
In 2003, Hurricane Fabian (Category 3) passed just 50 miles to the west of Bermuda. The storm swept away about 10% of the Cahow nesting burrows about a month before the birds were due to return to nest. The BDC and volunteers succeeded in constructing artificial burrows in time for the birds' return, and they have also placed burrows higher and attempted to lure the birds to nest in these higher burrows by playing recorded bird calls.
Every major hurricane clearly poses a threat to the survival of this endemic Bermudian species, now numbering more than 70 breeding pairs. Nonsuch Island, a vegetated nature reserve is a more sheltered location for petrel burrows and efforts are proceeding to encourage the birds to move there: artificial burrows are constructed and located on the island, and young birds have been moved there before fledging in the hopes that they will return to the burrows to breed in the future.
The Bermuda Petrel breeding season begins in late October, so if Hurricane Florence had ravaged the nesting burrows on the four tiny offshore islands, there would still be time for another quick artificial burrow building effort before the birds arrived. Let's hope this is the only big storm to blast Bermuda this season.
Sources consulted:
Thomas, Martin L.H. The Natural History of Bermuda. Bermuda Zoological Society: 2004.
Hurricane Torn Bermuda Rallies to Save Seabirds. Birdlife International, Sept 25, 2003
Egg Rock Update, 2005: Cahow: Castle Harbour Bermuda
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