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Pterodroma sandwichensis

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA AVES PROCELLARIIFORMES PROCELLARIIDAE

Scientific Name: Pterodroma sandwichensis
Species Authority: (Ridgway, 1884)
Common Name(s):
English Hawaiian Petrel

Assessment Information [top]

Red List Category & Criteria: Vulnerable B2ab(iv,v) ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Ainley, D., Baicich, P., Baker, P., Holmes, T., Morin, M., Penniman, J. & Wilson, A.
Facilitator/Compiler(s): Anderson, O., Benstead, P., Isherwood, I., Stattersfield, A., Stuart, T., Taylor, J., Temple, H.
Justification:
This species qualifies as Vulnerable because it has a very small breeding range. It is known from five locations in the main Hawaiian islands, and the future of at least two are in jeopardy (Mauna Loa and West Maui). Its limited distribution and declines primarily result from predation by introduced mammals and urbanisation.

Geographic Range [top]

Range Description: Pterodroma sandwichensis ranges in the central Pacific and breeds on the Hawaiian Islands (USA), where an estimate, supported by pelagic surveys, put the total population at 19,000 (range 10,600-34,400), including a best estimate of 4,500-5,000 breeding pairs (Spear et al. 1995, Ainley et al. 1997a). However, the discovery of previously unknown colonies in 2006-2007 may bring the total population closer to the upper estimate of 6,500-8,300 pairs (Spear et al. 1995). The observation of birds' movements by radar suggests that the total number on Maui exceeds the current estimate of 1,800 individuals (Cooper and Day 2003). Approximately 1,200 burrows are known in Haleakala Crater, Maui, although not all of these are used every year (J. Penniman in litt. 2007), and two small colonies are present in the West Maui Mountains but they are so far unquantified (Cooper and Day 2003, J. Penniman in litt. 2007), with numbers perhaps in the tens or low hundreds (D. Ainley in litt. 2007). On Hawai`i, small numbers breed on Mauna Kea and 40-50 pairs were present on Mauna Loa prior to 1995 (Ainley et al. 1997a, Simons and Hodges 1998). On Kaua`i, 1,600 pairs are indicated by observations of birds at a rafting site (Ainley et al. 1997a). On Moloka`i, 5-10 birds were heard calling in 1980, suggesting small numbers (Simons and Hodges 1998), but there has not been a concerted effort to estimate numbers on this island (D. Ainley in litt. 2007). Surveys in 2006-2007 located a colony in the cloud forests of Lanaihale on the north side of Lâna`i (P. Baicich in litt. 2007, A. Wilson in litt. 2007). This population probably numbers several thousand birds, based on the volume of calling during night time listening surveys in April and May along the Lana`ihale ridge at the highest point in the uplands, although only 14 burrows had been found by October 2007 (J. Penniman in litt. 2007). Surveys have so far been hampered by weather conditions and the risk of habitat disturbance (J. Penniman in litt. 2007).

Countries:
Native:
United States (Hawaiian Is.)
Vagrant:
Indonesia; Japan; Philippines
Present - origin uncertain:
French Polynesia; Kiribati; United States Minor Outlying Islands
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Spear et al. (1995) give a best estimate of 3,750-4,500 breeding pairs based on at-sea surveys. This roughly equates to 6,000-11,000 mature individuals, and 9,000-16,600 individuals in total. However, the discovery of possibly several thousand birds breeding on Lana`i during terrestrial surveys in 2006-2007 and two small colonies on West Maui (J. Penniman in litt. 2007), probably in the tens or low hundreds of birds (D. Ainley in litt. 2007), brings the estimated breeding population close to the upper estimate of 6,500-8,300 pairs calculated by Spear et al. (1995).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: On Maui, Mauna Kea and Mauna Loa, nesting takes place mainly between 2,000 and 3,000 m, in lava cavities with little vegetation nearby (D. Ainley in litt. 2007). Elsewhere, for example West Maui (J. Penniman in litt. 2007) and Kaua`i (N. Holmes in litt. 2007), it nests at lower elevations, amongst dense shrubs and ferns (D. Ainley in litt. 2007), or in native grasslands with bracken (Ainley et al. 1997a, Simons and Hodges 1998, P. Baker in litt. 1999). On Haleakala, Maui, birds nest in rock crevices and tunnels that are over 0.5 m deep, often exceeding two metres (J. Penniman in litt. 2007). Generally, the nest chamber can be from one to nine metres deep (Mitchell et al. 2005). Pairs nest in cavities in the volcanic terrain, in burrows beneath rocks or at the base of clay cliffs (N. Holmes in litt. 2007). At lower altitudes, they excavate burrows or nest in cavities often at the base of trees (Simons and Hodges 1998, P. Baker in litt. 1999, N. Holmes in litt. 2007), although many burrows on Lâna`i are not at the base of trees (J. Penniman in litt. 2007). On Lâna`i birds breed in dense uluhe fern habitat (Dicranopteris linearis and Diplopterygium pinnatum) and start breeding in March whereas on Haleakala, Maui, birds begin breeding in early February (Penniman et al. 2008). It takes each bird five to six years to reach maturity (Hess and Banko 2006). Most eggs are laid in May and June, with most young fledging by December (Mitchell et al. 2005). The diet comprises mostly fish and squid, with squid constituting c.50-75% of the food ingested (Simons and Hodges 1998). The species ranges in the north Pacific to around 50 N when foraging for chick provisioning (J. Penniman in litt. 2007). It has been found that at least some birds nesting on Lâna`i feed in waters around the Aleutian Islands, as shown through the use of tracking devices on several breeding individuals P. Baicich in litt. (2007. The species usually forages in mixed species flocks, typically over schools of predatory fish species (Mitchell et al. 2005).

Systems: Terrestrial; Marine

Threats [top]

Major Threat(s): Historically the species suffered declines through harvesting by Polynesians after they arrived c.1,800 years ago (Carlile et al. 2003). The species was eliminated from many islands in the archipelago, and it may already have been restricted to its current breeding range when Europeans arrived (Carlile et al. 2003). Nesting habitat has since been lost to urbanisation and degraded by feral goats and pigs. Nest burrows are trampled by feral goats, mouflon sheep and potentially chital Axis axis (Mitchell et al. 2005). The most serious current threat is predation by introduced vertebrates including feral cats, Barn Owls Tyto alba, rats, dogs, pigs and the small Asian mongoose Herpestes javanicus (although the latter is not yet established on Lâna`i). Nestlings are very susceptible to predation, as they cannot fly for more than 15 weeks after hatching (Hess and Banko 2006). The population on Hawai`i is probably declining as a result, and the south-east Mauna Loa colony may soon be lost (Simons and Hodges 1998). The species is currently threatened with habitat disturbance by goats, pigs and cattle (Carlile et al. 2003). On Lâna`i, habitat degradation caused by the invasive tree, strawberry guava Psidium cattleianum, may be the biggest threat to the long term survival of the colony (J. Penniman in litt. 2007). On occassion, fledglings become grounded after colliding with lights (Simons 1985), and mortality sometimes results from collisions with fences and powerlines (Cooper and Day 1998, Simons and Hodges 1998). Once on the ground, fledglings are unable to fly and are killed by cars or cats and dogs, or die from starvation or dehydration (Mitchell et al. 2005). The species may be threatened by plans for a field of wind generators on Lâna`i (A. Wilson in litt. 2007), although following the discovery of large numbers nesting on the island measures to minimise and mitigate any impact on the species are being developed (J. Penniman in litt. 2007). The species may be adversely affected by declines in the populations of large predatory fish that drive prey species to the surface (J. Penniman in litt. 2007). In addition, a significantly lower percentage of birds come ashore to nest during El Niño years (c.40% compared to c.65% normally) (C.N. Hodges per Carlile et al. 2003), suggesting that the species is sensitive to such disturbances in environmental conditions (Carlile et al. 2003).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
CMS Appendix I. On Maui, there is a long-term monitoring programme in the Haleakala National Park (Simons and Hodges 1998) and efforts are made to control introduced mammals. In 1976, a perimeter fence was put up around the main colony to exclude feral goats and pigs from the habitat (Carlile et al. 2003). The predator exclosures placed around the national park may have facilitated an increase in the number of birds in eastern Maui (Cooper and Day 2003). The trapping of rats started in 1968, and since 1997 rodenticides have been used (Carlile et al. 2003). Cats and mongooses have been controlled since 1981, and trapping of these species and rats continues to be carried out year-round (Carlile et al. 2003). On Lâna`i: colony delineation surveys are continuing (J. Penniman in litt. 2007), and as burrows are found they are included in basic breeding biology study; feral cats are being trapped and removed; studies on Tyto alba are being designed; a rat population assessment was due to begin in 2007, with control by rodenticide to be carried out subsequently; habitat restoration work may begin in January 2008; and public education projects will be implemented in 2008 (J. Penniman in litt. 2007). In 2006, a fence was completed to encircle a large portion of the breeding habitat on Lâna`i; the purpose was to exclude ungulates that damage the vegetation thus impacting the island's water supply (D. Ainley in litt. 2007). Simultaneously, a limited cat-trapping programme has been initiated in the fenced area (D. Ainley in litt. 2007). On Maui, Lâna`i, and Kaua`i, grounded fledglings are collected and released, although the benefit of doing this has yet to be confirmed as very few banded individuals have subsequently been encountered (D. Ainley in litt. 2007). Fencing erected for forest conservation has been modified to reduce collisions (Simons and Hodges 1998). On Kaua`i, auditory surveys to detect colonies are ongoing, and have included documenting the first known nesting sites on Kaua`i in the Upper Limahuli Preserve (N. Holmes in litt. 2007). Also on Kaua`i, street lighting is shielded in critical areas and lighting on some buildings has been modified to reduce collisions (Ainley et al. 1997b, Simons and Hodges 1998). A ruling brought by the U.S. Fish and Wildlife Service in 2006, under the U.S. Endangered Species Act, has enforced a campaign running since 2005, in which all non-essential lights on Kaua`i are required to be turned off or shielded between 15 September and 15 December when young birds leave their nests (Appel 2006). The island's electricity company is helping by darkening all of its 3,000 street lights, and shielding or turning some of them off. The company has also fitted large balls to power lines in an effort to reduce the number of birds that collide with the cables (Appel 2006). Significant improvements have beem made in reducing light attraction and collision, although there is still a considerable amount of new and existing infrastructure that requires modification (N. Holmes in litt. 2007). Methods are currently being developed to quantify the population on each island; surveys for colonies on West Maui are being carried out and surveys on Moloka`i were planned to begin in Spring 2008 (J. Penniman in litt. 2007).

Conservation Actions Proposed
Improve radar sampling for use as a population monitoring technique (D. Ainley in litt. 2007, J. Penniman in litt. 2007). Use passive integrated transponder (PIT) tags to study colony attendance by breeding pairs (J. Penniman in litt. 2007). Reduce collisions with power lines by making them more visible, burying them or moving them further inland where birds fly higher (Cooper and Day 1998). Ensure lighting does not attract petrels (Ainley et al. 1997b). Control predators in known colonies (M. Morin in litt. 2000), and improve measures for the declining colonies at Mauna Loa, Hawai`i (Carlile et al. 2003) and West Maui (D. Ainley in litt. 2007). Monitor breeding success (Carlile et al. 2003). Continue to retrieve grounded birds (Carlile et al. 2003), but conduct research to assess the effectiveness of rehabilitation methods (D. Ainley in litt. 2007). Continue to search for additional breeding areas (Carlile et al. 2003). Carry out further research into foraging range and feeding behaviour and investigate the species's vulnerability to human-induced mortality at sea (Carlile et al. 2003). Investigate the impact of the loss of tuna schools that the species depends upon for foraging (D. Ainley in litt. 2007). Undertake research into the potential effects of climate change on the species (Carlile et al. 2003).


Citation: BirdLife International 2012. Pterodroma sandwichensis. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 23 December 2014.
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