Pterodroma cahow

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	Procellariiformes	Procellariidae

Scientific Name:

Pterodroma cahow

Species Authority:

(Nichols & Mowbray, 1916)

Common Name/s:

English

–

Bermuda Petrel, Cahow

Assessment Information [top]

Red List Category & Criteria:

Endangered D ver 3.1

Year Assessed:

2008

Assessor/s

BirdLife International

Evaluator/s:

Butchart, S. & Mahood, S. (BirdLife International Red List Authority)

Justification:
Successful conservation has increased the population of this species, but it remains extremely small and the species consequently qualifies as Endangered. If the population continues to grow, the species will warrant downlisting to Vulnerable in due course.

History:

2006	–	Endangered
2004	–	Endangered
2000	–	Endangered
1994	–	Endangered
1988	–	Threatened

Geographic Range [top]

Range Description:	Pterodroma cahow once bred abundantly throughout Bermuda (to UK). It was thought extinct for almost three centuries, until reported (with specimens) during the first half of the 20th century. In 1951, 18 pairs were rediscovered breeding on suboptimal rocky islets (total area 1 ha) in Castle Harbour. Intensive management has resulted in slow but steady increases, and the population was estimated at 250 birds in 2005⁷, with 70 pairs fledging a record 40 young in 2003⁵, and 71 pairs fledging 35 young in 2005⁷. In the non-breeding season, birds probably move north into the Atlantic, following the warm waters on the western edges of the Gulf Stream². There are confirmed records off the coast of North Carolina, USA^1,3, and one bird was captured in the Azores in November 2002⁶.
Countries:	Native: Bermuda; United States Vagrant: Bahamas; Portugal
FAO Marine Fishing Areas:	Native: Atlantic – western central; Atlantic – northwest
Range Map:	(click map to view full version)

Population [top]

Population:	250 individuals, of which 71 breeding pairs, so minimum 142 mature adults (J. Madeiros in litt. 2005).
Population Trend:	Increasing

Habitat and Ecology [top]

Habitat and Ecology:	It formerly nested in soil burrows, but such habitat is not available on current breeding islands and it now nests in suboptimal, natural erosion limestone crevices and artificial burrows. The breeding season is January-June, and breeding success has increased from less than 5% per year in the 1950s to more than 25% per year in the 1990s². Ringing recoveries have shown that birds return to birds first return to breed four years after fledging⁸. The breeding grounds are not visited by birds between mid-June and mid-October².
Systems:	Terrestrial

Habitat and Ecology:

It formerly nested in soil burrows, but such habitat is not available on current breeding islands and it now nests in suboptimal, natural erosion limestone crevices and artificial burrows. The breeding season is January-June, and breeding success has increased from less than 5% per year in the 1950s to more than 25% per year in the 1990s². Ringing recoveries have shown that birds return to birds first return to breed four years after fledging⁸. The breeding grounds are not visited by birds between mid-June and mid-October².

Systems:

Terrestrial

Threats [top]

Major Threat(s):	The drastic population decline is attributed to habitat loss, exploitation and predation. Its recovery has been hampered by competition from White-tailed Tropicbird Phaethon lepturus for nest-sites. Light pollution from a nearby airport and NASA tracking station adversely affects nocturnal aerial courtship³. The threat of sea-level rise and increased storm activity appears real, with five or more major floods affecting burrows in the 1990s, after 25 years without significant problems³. Category three hurricane Fabian in 2003 overwashed three of the four breeding islets, damaging or destroying a significant number of nest burrows⁷. Increasing egg failure may be attributable to contaminants². Rats also swam to one breeding island in April 2005, but were successfully eradicated within two weeks without loss to the Cahows⁷.

Major Threat(s):

The drastic population decline is attributed to habitat loss, exploitation and predation. Its recovery has been hampered by competition from White-tailed Tropicbird Phaethon lepturus for nest-sites. Light pollution from a nearby airport and NASA tracking station adversely affects nocturnal aerial courtship³. The threat of sea-level rise and increased storm activity appears real, with five or more major floods affecting burrows in the 1990s, after 25 years without significant problems³. Category three hurricane Fabian in 2003 overwashed three of the four breeding islets, damaging or destroying a significant number of nest burrows⁷. Increasing egg failure may be attributable to contaminants². Rats also swam to one breeding island in April 2005, but were successfully eradicated within two weeks without loss to the Cahows⁷.

Conservation Actions [top]

Conservation Actions:	Conservation actions underway: CMS Appendix I. Since 1961, there has been management of nesting-grounds, including the creation of artificial burrows, periodic removal of rats and the elimination of nest-site competition from P. lepturus (by installing baffles over burrow entrances). As part of the Bermuda Conservation Programme, potential breeding islands (e.g. Nonsuch) have been reforested with native flora in an attempt to attract nesting petrels³. The Castle Harbour islands are a National Park and Nature Reserve⁷. In 2004 and 2005 efforts were made to attract adult Cahows, displaced from low-lying nest burrows destroyed by hurricane Fabian, on the main breeding islet to a new artificial burrow complex built on a more elevated section of the islet. Using a combination of a sound attraction system set up among the new nests and physicall translocation of adult Cahows from the destroyed sites, three pairs occupied burrows in the new complex by March, 2005⁷. A project is now underway to establish a new nesting colony on the Nonsuch Island Living Museum, which is much larger and contains more suitable breeding habitat than the present suboptimal breeding islets. The project involves physical translocation of chicks from the present breeding islets to a new complex of artificial burrows on Nonsuch, so that they will imprint on the new site and return when mature to establish their nests at the new location. In 2004, the trial year of the project took place with 14 chicks moved to Nonsuch, where they were fed and monitored every other day until departure, with all fledging successfully. In 2005, 21 chicks were translocated, with all again fledging successfully by mid-June. This project is scheduled to continue for three more years, with a target of 90 to 100 chicks in total being translocated over a five-year period⁷. Conservation actions proposed: Maintain all management activities at current nesting-grounds. Investigate whether contaminants are increasing egg failure². Continue to manage the new breeding colony on Nonsuch Island^2,5,7. Investigate the pelagic and foraging range of the species using new data logger technology⁷.

Conservation Actions:

Conservation actions underway:

CMS Appendix I. Since 1961, there has been management of nesting-grounds, including the creation of artificial burrows, periodic removal of rats and the elimination of nest-site competition from P. lepturus (by installing baffles over burrow entrances). As part of the Bermuda Conservation Programme, potential breeding islands (e.g. Nonsuch) have been reforested with native flora in an attempt to attract nesting petrels³. The Castle Harbour islands are a National Park and Nature Reserve⁷. In 2004 and 2005 efforts were made to attract adult Cahows, displaced from low-lying nest burrows destroyed by hurricane Fabian, on the main breeding islet to a new artificial burrow complex built on a more elevated section of the islet. Using a combination of a sound attraction system set up among the new nests and physicall translocation of adult Cahows from the destroyed sites, three pairs occupied burrows in the new complex by March, 2005⁷. A project is now underway to establish a new nesting colony on the Nonsuch Island Living Museum, which is much larger and contains more suitable breeding habitat than the present suboptimal breeding islets. The project involves physical translocation of chicks from the present breeding islets to a new complex of artificial burrows on Nonsuch, so that they will imprint on the new site and return when mature to establish their nests at the new location. In 2004, the trial year of the project took place with 14 chicks moved to Nonsuch, where they were fed and monitored every other day until departure, with all fledging successfully. In 2005, 21 chicks were translocated, with all again fledging successfully by mid-June. This project is scheduled to continue for three more years, with a target of 90 to 100 chicks in total being translocated over a five-year period⁷.

Conservation actions proposed:

Maintain all management activities at current nesting-grounds. Investigate whether contaminants are increasing egg failure². Continue to manage the new breeding colony on Nonsuch Island^2,5,7. Investigate the pelagic and foraging range of the species using new data logger technology⁷.

Citation:	BirdLife International 2008. Pterodroma cahow. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on 21 November 2009.
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