Short-tailed Shearwater

Ardenna tenuirostris

Order: Procellariiformes / Family: Procellariidae

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brown gray white medium seabird coastal migratory colonial common widespread

About the Short-tailed Shearwater

The Short-tailed Shearwater (Ardenna tenuirostris) is a remarkable seabird known primarily for its prodigious migratory journeys that span across the vast stretches of the Pacific Ocean. This species is a member of the Procellariidae family, which distinguishes itself with its robust build and adept flying skills. These birds are predominantly found nesting in the southern coastlines of Australia, where they form dense breeding colonies. The ecological role of the Short-tailed Shearwater is vital, as it contributes to the marine food web by serving as both predator and prey. During their time at sea, they feed on a variety of marine organisms, playing a role in controlling fish and krill populations. Their migratory patterns see them embark on trans-equatorial expeditions, reaching as far north as the Bering Sea during the austral winter months. This species, due to its extensive range and large populations, is an excellent indicator of ocean health. The Short-tailed Shearwater also holds cultural significance, particularly among the Indigenous communities of Tasmania, who have long harvested them sustainably. These birds are integral to the marine ecosystems, impacting nutrient cycles through their feeding and breeding behavior. Adapted to a life at sea, the Short-tailed Shearwater spends the majority of its life gliding over oceanic waters, only returning to land to breed. Their breeding season begins in September, when they return to their nesting sites in Australia to lay eggs and raise their young. The Short-tailed Shearwater's ability to cover vast distances in pursuit of suitable foraging grounds demonstrates not only their endurance but also the intricate connectivity of global ecosystems. Their role in nutrient transfer, through both their droppings and as prey for larger marine predators, helps sustain the delicate balance in their habitats. As climate change continues to impact marine environments, understanding the movements and behaviors of the Short-tailed Shearwater becomes increasingly important for conservation efforts.

The Short-tailed Shearwater belongs to the family Procellariidae, within the order Procellariiformes. These birds typically live average lifespan is 15-19 years, with a maximum recorded over 30 years..

How to Identify a Short-tailed Shearwater

The Short-tailed Shearwater is easily identified by its medium size, measuring approximately 40 to 45 centimeters in length with a wingspan ranging from 90 to 95 centimeters. Adult plumage is predominantly dark gray-brown, with slight variations depending on wear. The wings are long and narrow, designed for efficient gliding over the sea. The underparts are slightly lighter, which can be observed when the bird is in flight. Juvenile shearwaters closely resemble adults, though their plumage may appear fresher and more uniform. Male and female Short-tailed Shearwaters are similar in appearance, making sex differentiation in the field difficult without closer inspection. Their silhouette in flight is distinctive, with the wings held stiffly and slightly bowed, allowing for dynamic soaring above ocean swells. Unlike some other shearwater species, the Short-tailed Shearwater lacks the contrasting white underwing, which helps distinguish it from similar species such as the Sooty Shearwater. When perched, these birds exhibit a compact posture, often sitting low on their tarsi, which minimizes wind resistance. Their short tail, as their name suggests, is less conspicuous compared to other shearwaters.

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Short-tailed Shearwater Habitat and Range

Preferred Habitat

Short-tailed Shearwaters are primarily pelagic birds, spending most of their lives in open ocean environments. They nest on coastal islands and headlands with sandy or peaty soil, which allows them to excavate burrows for nesting. In Australia, their breeding colonies are most commonly found in Tasmania and Victoria. These birds prefer areas with sparse vegetation, as dense plant cover can hinder their take-off and landing. During the non-breeding season, they migrate to the northern Pacific Ocean, frequenting areas near Japan, Alaska, and the Aleutian Islands. They favor cold and temperate waters, often associating with upwellings where prey is abundant. Despite their extensive migrations, Short-tailed Shearwaters rarely venture into urban environments or inland areas, as they are highly adapted to marine life.

Geographic Range

The Short-tailed Shearwater's breeding range is concentrated along the southern coast of Australia, with the largest colonies located in Tasmania and the Bass Strait islands. During the austral winter, these birds migrate to the northern hemisphere, traveling vast distances to reach feeding grounds in the North Pacific Ocean. Key areas include the Bering Sea, the Sea of Okhotsk, and the coastal waters off Japan and Alaska. This migration covers over 15,000 kilometers each way. These shearwaters follow specific migratory corridors, using prevailing winds and ocean currents to aid their journey. During migration, they are often seen in large flocks, particularly in areas where food is abundant. Population density is highest near their breeding colonies during the nesting season, and they are also concentrated in feeding hotspots along their migratory route.

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What Does the Short-tailed Shearwater Eat?

The diet of the Short-tailed Shearwater consists mainly of small fish, squid, and krill, with variations depending on season and location. During the breeding season, they forage in the nutrient-rich waters off southern Australia, where they primarily consume krill and small fish. In the non-breeding season, their diet shifts slightly to include more squid, reflecting the prey availability in the northern Pacific. Foraging techniques include surface seizing and plunge diving, with birds often seen pattering on the water's surface to capture prey. Prey size typically ranges from 1 to 10 centimeters. Feeding often occurs during the early morning and late afternoon, although they can be opportunistic feeders, taking advantage of any available food source. These birds are known to associate with cetaceans and other seabirds, taking advantage of prey driven to the surface.

Short-tailed Shearwater Behavior and Social Structure

Short-tailed Shearwaters are highly social birds, often seen in large flocks, particularly during migration. Their social structure during the breeding season is colony-based, with thousands of pairs nesting in close proximity. Territorial behavior is limited to the immediate area surrounding their nest burrow. Courtship displays involve synchronized flight patterns and vocalizations, strengthening pair bonds. These birds are known for their impressive flocking patterns, often forming dense aggregations while foraging at sea. In response to predators, adult shearwaters rely on their agile flight to evade threat, while chicks and eggs are vulnerable to predation by gulls and skuas. Daily activity patterns vary with feeding often taking place in the early morning and late afternoon, although they can be active at any time of day. Nighttime activity increases during the breeding season when adults return to their burrows under the cover of darkness.

Short-tailed Shearwater Nesting and Reproduction

Short-tailed Shearwaters nest in burrows, which they excavate in sandy or peaty soil. These burrows are typically 1 to 2 meters in length, providing protection for the single egg laid during the breeding season. Nesting sites are often at elevations close to sea level on coastal islands. The clutch size is invariably one egg, which is incubated by both parents for approximately 52 days. Once hatched, the chick is brooded and fed regurgitated food by both parents. The fledging period lasts about 90 days, during which time the chick grows rapidly, preparing for its first migration. Parental roles are shared equally, with shifts lasting several days at sea to forage. Short-tailed Shearwaters typically have one brood per year, with breeding commencing in September and chicks fledging by April.

Short-tailed Shearwater Sounds and Vocalizations

The vocalizations of the Short-tailed Shearwater are most commonly heard at night within breeding colonies. Their primary call is a soft, rhythmic cooing, interspersed with harsher squawks. These sounds serve as communication between mates and signals within the colony. Alarm calls are sharper and louder, often used to deter predators. Unlike many songbirds, the Short-tailed Shearwater does not produce a melodic song, as its vocalizations are more functional. The dawn chorus in a shearwater colony is a cacophony of coos and squawks, reminiscent of distant, murmuring crowds.

Interesting Facts About the Short-tailed Shearwater

1Short-tailed Shearwaters undertake one of the longest migrations of any bird, covering over 30,000 kilometers annually.
2These birds are known locally in Australia as 'muttonbirds,' a name derived from the taste of their meat.
3The Short-tailed Shearwater can dive up to 10 meters deep to catch prey, showcasing its adept foraging skills.
4In Tasmania, the practice of muttonbirding by Indigenous peoples is a culturally significant activity that dates back thousands of years.
5During migration, Short-tailed Shearwaters can be seen in flocks numbering in the tens of thousands, creating a spectacular sight.
6These birds can live for over 20 years, with some individuals recorded breeding well into their second decade.
7Short-tailed Shearwaters possess a highly developed sense of smell, aiding them in locating food over vast oceanic distances.

Short-tailed Shearwater Conservation Status

According to the IUCN, the Short-tailed Shearwater is currently listed as Least Concern due to its large population and extensive range. However, threats such as climate change, pollution, and fishing bycatch pose significant risks. Conservation efforts focus on habitat protection and monitoring population trends to ensure sustainability. Historical population changes have seen fluctuations due to human harvesting and introduced predators. Ongoing research and conservation initiatives aim to mitigate these threats and protect key breeding sites.