ʻEwaʻewa or Sooty Tern

Sterna fuscata

SPECIES STATUS:
State recognized as Indigenous

NatureServe Heritage Rank G5 - Secure

North American Waterbird Conservation Plan –
Moderate Concern

Regional Seabird Conservation Plan - USFWS 2005

Species Information

The ‘ewa‘ewa or sooty tern is an abundant and gregarious tern (Family: Laridae) with a pantropical distribution, and is able to remain on the wing for years. Eight ‘ewa‘ewa (sooty tern) subspecies are recognized, and one (S. f. oahuensis) breeds in Hawai‘i. Individuals have long, slender wings and a deeply forked tail. Adult males and females are blackish above, except for white forehead and white on the edges of the outer most tail feathers, and entirely white below. The sharp bill, legs, and feet are black. Flight is characterized by powerful flapping, gliding and soaring, capable of long-distance migration and breeding adults remain aloft between breeding seasons. Generally forages in large mixed-species feeding flocks, typically feeding over schools of predatory fishes, especially yellowfin tuna (Neothunnus macropterus) and skipjack tuna (Katsuwonus pelamis). ‘Ewa‘ewa (sooty tern) feed primarily by seizing prey from the water or air while on the wing, infrequently by shallow dives; species’ plumage has poor waterproofing and easily becomes waterlogged. In Hawai‘i, ‘ewa‘ewa (sooty tern) diet consists of squid, goatfish, flying fish, and mackerel scad. Nests in large, dense colonies consisting of thousands to a million pairs of terns. Individuals return to the natal colony to breed, some long-term pair bonds have been documented, and breeders prefer to return to previous nest locations. Nests are shallow scrapes often lined with bits of shell or vegetation. The timing of breeding varies among years and locations, even within Hawai‘i, but generally, eggs are laid beginning of February and most birds fledge by July. Both parents incubate single egg and brood and feed the chick. Parents continue feeding young for two weeks after fledging and young remain aloft until they return to breed. Birds first breed between four and ten years of age and the oldest known individual was 32 years old.

Location & Habitat

‘Ewa‘ewa (sooty tern) breed throughout the NWHI and on Moku Manu off of the island of O‘ahu. Outside of Hawai‘i, ‘ewa‘ewa (sooty tern) breed on most islands throughout the world’s tropical oceans. Outside the breeding season, ‘ewa‘ewa (sooty tern) are highly pelagic.

In Hawai‘i, the population is estimated at greater than one million breeding pairs with the largest populations occurring on Laysan (500,000 pairs) and Lisianski (500,000 pairs). Worldwide population is estimated at between 60 and 80 million breeding pairs.

Location & Habitat

Terrestrial: ‘Ewa‘ewa (sooty tern) breed on oceanic islands and atolls. The nest is usually on sandy substrates with sparse vegetation.

Marine: Pelagic.