Puffinus auricularis newelli (Endemic)

Hawaiian: Ao

Family: Procellariidae

Federally listed as Threatened

State listed as Threatened

IUCN Ranking - Endangered

§         Description

§         Distribution

§         Breeding Ecology

§         Feeding Ecology

§         Threats and Status

§         References

Newell's chick, Kilauea Point  (Photo: B. Zaun)

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The Newell’s Shearwater belongs to the “Manx-type shearwater” group, a species complex that has undergone frequent taxonomic revision. Puffinus auriculars newelli is a subspecies endemic to the Hawaiian Islands. The Newell's Shearwater is a fairly small black and white shearwater with a dark pointed tail. Their upperparts are black, occasionally with a brownish hue and white underparts while their underwing is white with a narrow black border and black primary shafts on the underside. The black on their face extends below their eye covering their ear coverts and lores. The white from their underparts extends onto the sides of the rump and this is very prominent when a bird is seen from above. As with most shearwater species, they have a dark narrow bill with a hooked tip.  

In flight, the species can be distinguished from the similar Wedge-tailed Shearwater (Puffinus pacificus) by their distinctive flight-pattern (rapid flapping of stiffly-held wings interspersed with short glides).

Breeding (April-November)

This species nests only in the main Hawaiian Islands on Kauai (Na Pali Coast, Lumahai Valley, Wainiha Valley, Kalaheo, Moalepe, at the base of  Waialeale, and at Kilauea Point NWR), Molokai (Waialea and Waikolu Valleys), and Hawaii (several areas in the Puna District, along the Hamakua coast, and Waipio Valley). Additionally, Newell’s may nest in small numbers on Maui, Oahu and Lehua (off Niihau), but breeding has not been confirmed. Numbers of both colonies and individuals are greatest on Kauai, the only major island without mongoose. 

During the breeding season, low densities of birds occur short distances west and north of Hawaii (to about 25°N) and some Newell’s can be found within a few hundred kilometers of their breeding colonies. However, most individuals occur in waters as far as 3,000 km to the east.

Marine

Newell’s Shearwaters are well known by the Pacific tuna industry for their association with tuna and large billfish. This species is highly pelagic; found flying where the thermocline reaches deep and the ocean measures more than 2,000 meters. Newell’s can be found in the deepwater regions of the Equatorial countercurrent all year round, to the south (up to 25º N), and east (to about 120ºW) of the Hawaiian chain. Their range extends during El Nino events.

Newell’s Shearwater colonies are typically found at high elevations. This may not have always been the case as historical accounts mention colonies at lowland sites. The fact that known Newell’s Shearwater colonies are remote and/or occur on slopes greater than 65 percent suggests that loss of habitat to development and predation by nonnative mammals may have constrained their habitat use. Currently, colonies are typically located in areas of open native forest dominated by ohia (Metrosideros polymorpha) with a dense understory of uluhe fern (Dicranopteris linearis). Burrows are most commonly placed at the base of trees, where the substrate may be easier for the birds to excavate. At least one colony on Kauai nests in a vertical cliff face, where birds are using rock crevices rather than burrows. 

The Newell’s Shearwater breeding season begins in April, when birds return to prospect for nest sites. A pre-laying exodus follows in late April, and highly synchronized egg-laying occurs in June.  Pairs produce one egg, and the average incubation period may be somewhat longer than the 51 days documented for the closely related Manx shearwater. Both parents incubate the egg, and brood and feed the nestling. Parents forage hundreds of kilometers offshore and return to the colony at night to feed their chick. Chicks fledge 90 days after hatching and no postfledging care is provided. Most fledging occurs in October, but some birds fledge in November. First breeding occurs at approximately six years of age, and in comparison with similar species, the rate of non-breeding is high even among experienced adults occupying the colony during the summer breeding season. 

§         Feeding guild – TUNA BIRD

§         Food capture – This species plummets into fish schools from their aerial vantage point and feeds mainly by pursuit-plunging; individuals dive into the water and swim using their partly folded wings for propulsion. They can swim to depths of at least 10 m and swallow multiple prey items. They are not seen scavenging.

§         Foraging Distribution – They frequent incoming oceanic storm fronts that churn up rich food resources.

§         Microhabitat for foraging – Newell's Shearwaters forage in association with big predatory fish (e.g. tuna), which push smaller prey species up to the surface making them available.

§         Diet – Food items are not yet well known, but likely include fish, plankton and squid. Squid was the only prey regurgitated by adult Newell’s Shearwaters trapped at entrances of their burrows on Kauai.

Population numbers are difficult to estimate because of the remoteness and difficult terrain of nesting colonies. In the early 1990s, the population estimate based on at sea densities was 84,000 individuals (included adults and non-breeding birds). Estimates based on demographic data suggest a population of 14,600 breeding pairs, 75% of which nest on Kauai; estimates based on radar detections suggest this number is valid. Since these estimates were made, the population has been undergoing a startling decline. Population models incorporating the best estimates of breeding effort and success yielded a population decreasing at a rate of 3.2% annually. When variables describing the anthropogenic mortality suffered by Newell’s Shearwaters (predation, light attraction, and collision) were included, these models predicted a population decline of 30% to 60% over 10 years. There is no specific data on longevity for this species, but other shearwaters may reach 30 years of age or more.

Main threats to the species include:

§         Predation – No terrestrial mammalian predators are native to the Hawaiian Islands, so this species is incapable of defending itself or its nest from mammals such as rats (Rattus spp.), cats (Felis sylvestris), dogs (Canis familiaris), pigs (Sus scrofa), and mongooses (Herpestes auropunctatus). Predation therefore is a serious threat to adult seabirds and their eggs and chicks. Small, burrow-nesting species such as shearwaters and petrels are especially vulnerable. Predation by cats on adult and subadult Newell’s Shearwaters has been documented on Kauai, and rats are thought to prey on shearwater eggs and chicks. The presence of mongooses on Kauai is questionable, but would have a devastating effect on the species. The nonnative barn owl (Tyto alba) also preys on adult Newell’s Shearwaters as they return to their colonies.

§          Light attraction and collision – Urbanization on Kauai has been positively correlated with increased groundings or “fallout” of fledgling shearwaters on their first nocturnal flight from the burrow to the sea. The young birds are attracted to and blinded by light sources, and they frequently collide with power lines, buildings, cars, and other obstacles, or simply fall to the ground exhausted after fluttering around lights for long periods. Adult shearwaters apparently are not attracted to lights to the same degree as fledglings, but adults do collide with power lines. In 2003, KIUC completed shielding all streetlights they operate on Kauai, but there remain many lights to attract fledgling shearwaters, for example, harbor, airport, hotel, and stadium lights around the island. Since 1978, the organization Save Our Shearwaters (http://www.kiuc.coop/save_our_shearwaters.htm ) has banded and released about 23,000 shearwaters picked up by Kauai residents and brought to stations set up around the island.  Although undoubtedly important, the specific effects of this rescue effort on the shearwater population are unknown - few bands from SOS-released birds have been recovered.

§         Habitat degradation and loss – Newell’s Shearwater habitat is degraded by feral ungulates such as pigs and goats, which now are managed as game species. Pigs and goats alter the vegetation structure, facilitate the invasion of nonnative plants (and perhaps of predators), and crush burrows and compact the soil. Invasive nonnative plants, such as Albizia falcataria, Psidium spp., and Rhodomyrtus tomentosa, displace native vegetation and can completely alter vegetation structure and substrates typical of shearwater habitat. For example, the habitat at the Kaluahonu colony (southeastern Kauai) has been almost completely and perhaps irreversibly transformed in just a few years and is now dominated by nearly pure and impenetrable stands of Rhodomyrtus tomentosa and Psidium spp. Intensive surveys indicate that the colony has been abandoned entirely.

§         Fisheries – In Hawaii, development overfishing may directly or indirectly harm seabird populations; harvest of skipjack and yellowfin tuna (Thunnus albacares) could eliminate predatory fish needed to drive prey species to surface. Also, live bait needed for the fishery could potentially decrease prey items. Development of a squid fishery could also impact Newell’s Shearwaters.

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Reed, J.R., Sincock, J.L.., and Hailman, J.I. 1985. Light attraction in endangered procellariiform birds: reduction by shielding upward radiation. Auk. 102: 377-383. http://elibrary.unm.edu/sora/Auk/v102n02/p0377-p0383.pdf

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