Pākalakala- Gray-backed Tern
Sterna lunata
| Stated-recognized | Indigenous |
| NatureServe Heritage Rank | Apparently Secure |
| North American Waterbird Conservation Plan |
Moderate concern |
| Regional Seabird Conservation Plan |
USFWS 2005 |
The Pākalakala or Gray-backed Tern (Family: Laridae) is endemic to the central Pacific and breeds on small and remote islands and atolls, however, its historical and current distribution are poorly known. Adults are mostly slate gray above and white below with a black crown and nape. Forehead has a narrow white patch that is continuous with white eye-brow that extends above and past eye and is completely bordered with black. Flight is direct and graceful and body appears to move up and down with each wing beat. Outside the breeding season, may remain in flight continuously.
Often forages with ‘Ewa‘ewa or Sooty Terns (S. fuscata) and ‘Ua‘u kani or Wedge-tailed Shearwaters (Puffinus pacificus). Pākalakala (Gray-backed Terns) feed mainly by plunge diving or by dipping the surface while hovering. Diet primarily consists of fish, especially five-horned cowfish, juvenile flyingfish, goatfish, herring, and dolphinfish, but also eats squid, crustaceans, mollusks, and marine and terrestrial insects. Pākalakala (Gray-backed Terns) nest in shallow depressions in sand or gravel, and like most seabirds lay a single egg per season. In Hawai‘i, nesting season varies from year to year, but most eggs are laid in February and March and most nestlings fledge by late July. Both males and females incubate egg, and brood and feed the chick. Oldest known bird was 25 years old.
DISTRIBUTION: Pākalakala (Gray-backed Terns) breed throughout NWHI, and a few pairs have been recorded breeding on Moku Manu off of the island of O‘ahu. Outside of Hawai‘i, Pākalakala (Gray-backed Terns) nest on the Marianas, Howland and Baker, Johnston, Wake, Jarvis, Line Islands, American Samoa, the Marquesas, and Tuamotu. Non-breeding distribution includes the central Pacific Ocean.
ABUNDANCE: In Hawai‘i, population estimated at 44,000 breeding pairs, with largest populations occurring on Lisianski (20,000 pairs), Nihoa (12,000 pairs), and Laysan (10,000 pairs). Worldwide population unknown but likely on the order of 70,000 breeding pairs.
LOCATION AND CONDITION OF KEY HABITAT: Terrestrial: Pākalakala (Gray-backed Terns) breed on remote islands and atolls. Nests are constructed in a variety of habitats (e.g., rocky ledges, open, sandy beaches) but usually at the base of shrubs or refuse. On Midway and Kure, individuals nest on runways. Nests are typically shallow depressions in sand or gravel and in surf zones, making them vulnerable to storm tides. Marine: Pelagic.
The management goals are important to Pacific seabird conservation: maintain, protect, and enhance habitat; eradicate or control non-natives; minimize bycatch and other negative effects of fishing; improve the effectiveness of oil spill response efforts; identify contaminants and hazardous substances; and minimize the effects of powerlines, towers, wind turbines and lights (USFWS 2005). The goal of these management actions is not only to protect seabird populations and their breeding colonies, but also to reestablish former breeding colonies thereby reducing the risk of extinction. Past actions have included efforts to mitigate the impact of longline fisheries and predator control.
Humans
Historically, wanton killing for feathers (i.e., millinery trade) greatly reduced populations. Populations extirpated from Johnston, Wake, and Marcus islands by Japanese feather hunters at the turn of the last century are only recently being recolonized. Untold numbers were killed as a result of military activities in the Pacific during World War II. Between 1954 and 1964, 54,000 albatross were killed on Midway to reduce the risk of collisions with aircraft. In 1909, 300,000 birds were killed on Laysan Island. Prior to banning drift net fisheries in 1993, thousands were killed annually. In the 1990s, longline fisheries killed thousands annually.
Introduced Predators
Like all seabirds, adults and nests are susceptible to predation by rats (Rattus spp.), and feral cats (Felis silvestris). All sites in NWHI are free of rats and cats.
Human Disturbance
Pākalakala (Gray-backed Terns) are sensitive to nest disturbance, and flush from nests when humans approach. Exposed eggs and chicks are vulnerable to predation by ‘Iwa or Great Frigatebirds (Fregata minor), ‘Akekeke or Ruddy Turnstones (Arenaria interpres), Kioea or Bristle-thighed Curlews (Numenius tahitiensis), and Laysan (Telespiza cantans) and Nihoa (T. ultima) Finches.
Manmade Structures
On Kure, collisions with man-made structures have resulted in mortality .
