Sooty Tern (Onychoprion fuscatus)

Common Name: Sooty Tern

Scientific Name: Onychoprion fuscatus
SizeDietRange in HawaiiStatus in Hawaii
12 in. - 15 in.small fish and squidOahuLeast Concern

Sooty Tern is known as the “Ewa’ewa” in Hawaiian language. The term “tern” is used to describe a group of seabirds that are known for their long, pointed wings and graceful, tern-like flight.

Sooty Terns are considered special in Hawaii for a few reasons. Firstly, they have a significant breeding population in the state, with an estimated 500,000-1,000,000 pairs on Midway Atoll and French Frigate Shoals.

Sooty Tern

Appearance

Sooty tern gliding
Sooty tern gliding | image by patrickkavanagh via Flickr | CC BY 2.0

Sooty Terns, are seabirds that are known for their dark, sooty-gray plumage. They have a white forehead and a white patch behind the eye. They have a long, forked tail and long, pointed wings.

Sooty Terns  have a dark bill and legs. They are about 12-15 inches (30-38 cm) in length and have a wingspan of about 27-31 inches.  They have a weight of about 6.5 – 8.8 ounces (0.185 – 0.25 pounds).

Diet

Sooty Terns primarily feed on small fish and squid. Their diet may also include crustaceans and other marine invertebrates. They typically forage by diving into the water from a height of up to 50 meters, and can also pick prey from the surface of the water.

Sooty Terns are known to follow schools of fish and are able to locate food using both visual and auditory cues. They feed both during the day and at night, and are known to travel large distances in search of food.

Behavior

Sooty Terns are highly social birds that form large colonies for breeding. They are known for their loud, piercing calls and are active during the day and at night.

During breeding season, Sooty Terns form monogamous pairs and both parents take turns incubating the eggs and caring for the chicks. After hatching, the chicks are tended to by both parents and other adults in the colony, and they fledge at around 6-8 weeks of age.

When they are not breeding, Sooty Terns are highly migratory, and they travel long distances in search of food. They are known to fly as far as 10,000 km (6,200 mi) from breeding colonies to feeding grounds.

Sooty Terns are known to be highly vocal birds, they have different calls for different activities like mating, nesting, feeding etc. They also have a synchronized behavior when it comes to nesting, they lay eggs and hatch at the same time.

Nesting

Flocks of sooty tern
Flocks of sooty tern | image by Dr Mary Gillham Archive Project via Flickr | CC BY 2.0

Sooty Terns typically nest in large colonies on sandy or rocky islands and beaches. The colonies can be quite dense, with nests placed close together. They are known to nest on both natural and man-made structures, such as on the ground, in crevices or burrows, or on flat surfaces like buildings or bridges.

Habitat

Sooty Terns can be found in tropical and subtropical regions around the world. They typically breed on sandy or rocky islands and beaches, and are known to nest on both natural and man-made structures, such as on the ground, in crevices or burrows, or on flat surfaces like buildings or bridges. They typically return to the same breeding location year after year.

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Range

In Hawaii, they can be found breeding on the small island of Moku Manu, which is located off the coast of Oahu in addition to Midway Atoll and French Frigate Shoals in the Hawaiian islands.

Conservation Status

The species has been listed as a “species of least concern” by the International Union for Conservation of Nature (IUCN) due to its large global population and wide range, however, in Hawaii, its breeding colonies are facing threats such as habitat loss, predation and human disturbance.

Interesting Facts

1. Incredibly long migrations

Sooty terns are known for their incredibly long migrations, where they travel thousands of miles between their breeding and non-breeding sites. They breed in large colonies on remote islands and atolls in tropical and subtropical oceans, such as the Caribbean and the Pacific.

2. Very high reproductive rate

They are known for their high reproductive rate, with some pairs raising up to three broods per year. This is possible because sooty terns have a short incubation period, and both parents take turns incubating the eggs and caring for the chicks.

3. Long-lived species

Sooty terns are a long-lived species, with a lifespan of over 20 years in the wild. This is relatively long for a bird species, especially when compared to other seabirds, many of which have shorter lifespans. The long lifespan of sooty terns is likely an adaptation to the harsh conditions of the remote islands and atolls where they breed.

4. Aerial acrobatic displays

Sooty terns are known for their aerial acrobatic displays, which they use during courtship and territorial displays. These displays are a combination of complex aerial maneuvers and vocalizations, which are performed by both males and females. They typically occur during the breeding season, when the birds are establishing and defending their territories, and attracting a mate.

5. Highly social birds

Sooty terns are highly social birds, and they have a complex system of vocalizations and displays that they use to communicate with each other. These birds use a wide range of vocalizations, including calls, screams, and songs, to communicate with other birds in their colony.

Frequently Asked Questions:

How many broods do Sooty Terns raise per year?

Sooty Terns can raise up to three broods per year.

What is the migration pattern of Sooty Terns?

Sooty Terns breed in colonies on remote islands and atolls and migrate to non-breeding sites, which can be located thousands of miles away, in the open ocean.

What is the global population of Sooty Terns?

The global population of sooty terns is estimated to be around 20 million individuals.