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For other uses, see Shearwater (disambiguation).

Shearwaters
Great shearwater
Great shearwater
Scientific classificationEdit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Procellariiformes
Family: Procellariidae
Diversity

3 genera and c. 30 species

Genera

Shearwaters are medium-sized long-winged seabirds in the petrel family Procellariidae. They have a global marine distribution, but are most common in temperate and cold waters, and are pelagic outside the breeding season.

Description

[edit]

These tubenose birds fly with stiff wings and use a "shearing" flight technique (flying very close to the water and seemingly cutting or "shearing" the tips of waves) to move across wave fronts with the minimum of active flight. This technique gives the group its English name.[1] Some small species like the Manx shearwater are cruciform in flight, with their long wings held directly out from their bodies.

Behaviour

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Movements

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Many shearwaters are long-distance migrants, perhaps most spectacularly sooty shearwaters, which cover distances in excess of 14,000 km (8,700 mi) from their breeding colonies on the Falkland Islands (52°S 60°W) to as far as 70° north latitude in the North Atlantic Ocean off northern Norway, and around New Zealand to as far as 60° north latitude in the North Pacific Ocean off Alaska. A 2006 study found individual tagged sooty shearwaters from New Zealand migrating 64,000 km (40,000 mi) a year,[2] which gave them the then longest known animal migration ever recorded electronically (though subsequently greatly exceeded by a tagged arctic tern migrating 96,000 km (60,000 mi)[3]). Short-tailed shearwaters perform an even longer "figure of eight" loop migration in the Pacific Ocean from Tasmania to as far north as the Arctic Ocean off northwest Alaska. They are also long-lived: a Manx shearwater breeding on Copeland Island, Northern Ireland, was (as of 2003/2004) the oldest known wild bird in the world; ringed as an adult (when at least 5 years old) in July 1953, it was retrapped in July 2003, at least 55 years old (also now exceeded, by a Laysan albatross). Manx shearwaters migrate over 10,000 km (6,200 mi) to South America in winter, using waters off southern Brazil and Argentina, so this bird had covered a minimum of 1,000,000 km (620,000 mi) on migration alone.

Following the tracks of the migratory Yelkouan shearwater has revealed that this species never flies overland, even if it means flying an extra 1,000 km. For instance, during their seasonal migration towards the Black Sea they would circumvent the entire Peloponnese instead of crossing over the 6 km Isthmus of Corinth.[4]

Breeding

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Shearwaters come to islands and coastal cliffs only to breed. They are nocturnal at the colonial breeding sites, preferring moonless nights to minimize predation. They nest in burrows and often give eerie contact calls on their night-time visits. They lay a single white egg. The chicks of some species, notably short-tailed and sooty shearwaters, are subject to harvesting from their nest burrows for food, a practice known as muttonbirding, in Australia and New Zealand.

Feeding

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Shearwaters feed on fish, squid, and similar oceanic food. Some will follow fishing boats to take scraps, commonly the sooty shearwater; these species also commonly follow whales to feed on fish disturbed by them. Their primary feeding technique is diving, with some species diving to depths of 70 m (230 ft).[2] Shearwaters defecate more often than other seabirds, typically between once every four to ten minutes. They excrete five percent of their body mass every hour, generally done while flying, rather than while resting on water.[5][6]

Taxonomy

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There are about 30 species: a few larger ones in the genera Calonectris and Ardenna and many smaller ones in Puffinus. Recent genomic studies show that Shearwaters form a clade with Procellaria, Bulweria and Pseudobulweria.[7] This arrangement contrasts with earlier conceptions based on mitochondrial DNA sequencing. [8][9][10]

List of species

[edit]

The group contains 3 genera with 32 species.[11]

There are two extinct species that have been described from fossils.

Phylogeny

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Phylogeny of the shearwaters based on a study by Joan Ferrer Obiol and collaborators published in 2022. Only 14 of the 21 recognised species in the genus Puffinus were included.[12]

Puffinus

Christmas shearwater Puffinus nativitatis

Fluttering shearwater Puffinus gavia

Hutton's shearwater Puffinus huttoni

Audubon's shearwater Puffinus lherminieri

Barolo shearwater Puffinus baroli

Boyd's shearwater Puffinus boydi

Manx shearwater Puffinus puffinus

Balearic shearwater Puffinus mauretanicus

Yelkouan shearwater Puffinus yelkouan

Little shearwater Puffinus assimilis

Subantarctic shearwater Puffinus elegans

Tropical shearwater Puffinus bailloni

Black-vented shearwater Puffinus opisthomelas

Newell's shearwater Puffinus newelli

Calonectris

Streaked shearwater Calonectris leucomelas

Cape Verde shearwater Calonectris edwardsii

Cory's shearwater Calonectris borealis

Scopoli's shearwater Calonectris diomedea

Ardenna

Buller's shearwater Ardenna bulleri

Wedge-tailed shearwater Ardenna pacifica

Short-tailed shearwater Ardenna tenuirostris

Sooty shearwater Ardenna grisea

Great shearwater Ardenna gravis

Flesh-footed shearwater Ardenna carneipes

Pink-footed shearwater Ardenna creatopus

References

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Shearwater

View on Grokipedia
from Grokipedia
Shearwaters are medium-sized, long-winged oceanic birds in the family , closely related to and fulmars, renowned for their characteristic low, skimming flight over waves that gives the group its name. These tubenosed seabirds possess external nasal tubes for salt excretion, hooked bills adapted for grasping prey, and streamlined bodies suited to a pelagic . Comprising around 30 across genera such as , Ardenna, and Calonectris, shearwaters exhibit a nearly , though they are most abundant in temperate and subtropical seas of the Atlantic, Pacific, and Indian Oceans. Shearwaters are highly migratory, with many species traveling tens of thousands of kilometers annually between remote island breeding colonies and distant foraging areas, often following ocean currents and upwellings rich in prey. They primarily feed on fish, squid, and crustaceans captured by surface-seizing or shallow dives, foraging in flocks that can number in the millions during non-breeding seasons. Breeding occurs nocturnally in burrows or crevices on predator-free islands, with single-egg clutches incubated for about two months; fledglings undertake independent migrations shortly after fledging. While numerous species maintain stable or abundant populations—such as the (Ardenna tenuirostris) with millions of breeding pairs—others face significant threats from commercial fisheries , plastic pollution, and at nesting sites, leading to classifications ranging from Least Concern to Critically Endangered by conservation authorities. Notable examples include the critically endangered Newell's shearwater ( newelli), restricted to , and the critically endangered Balearic shearwater ( mauretanicus), which migrates across the Mediterranean and Atlantic. Ongoing research emphasizes their ecological role in marine food webs and the need for international protections to mitigate human impacts on these far-ranging mariners.

Description

Physical Characteristics

Shearwaters are medium-sized, long-winged seabirds belonging to the family , with body lengths typically ranging from 25 to 56 cm and weights from 170 to 1100 g, though these measurements vary significantly across species. For instance, the smallest species, such as the little shearwater ( assimilis), measure about 25–30 cm in length and weigh 220–260 g, while larger ones like (Calonectris borealis) reach 45–56 cm and 700–1060 g. Smaller species generally fall at the lower end of this spectrum, contrasting with the bulkier Calonectris genus. Characteristic of the family, shearwaters possess tubular nostrils positioned atop their bills, which facilitate olfaction for detecting prey and navigating over vast ocean expanses. Their bills are strong and hooked at the tip, adapted for grasping fish, squid, and crustaceans from the water's surface or during shallow dives. The feet are fully webbed, enabling efficient propulsion through water as an aid to swimming and in marine environments. Shearwater plumage is generally dull and adapted for life at , featuring dark gray to black upperparts and white underparts in most species, though variations occur. Some, like the (Ardenna grisea), exhibit all-dark , while others display mottled patterns on the head or underwing coverts. undergoes a complete annual molt, often catastrophically after breeding, replacing feathers over several weeks to maintain waterproofing and insulation during non-breeding migrations. is minimal, with no notable differences in between males and females; however, males are slightly larger in body size and bill dimensions in species such as . A representative example is the ( puffinus), which measures 30–38 cm in length and weighs 350–575 g, with its slender body and long, narrow wings contributing to a posture in flight, where the wings extend perpendicular to the body for efficient gliding.

Flight Adaptations

Shearwaters are renowned for their flight technique, a highly efficient strategy that minimizes wing flapping and conserves energy during long-distance travel over oceans. This method relies on exploiting vertical wind gradients generated by surface waves, where birds execute repeated cycles of ascent into faster headwinds to gain and descent into slower tailwinds to maintain speed. The resulting flight path features horizontal zigzags combined with vertical undulations, typically at heights of 5–20 meters above the water, allowing shearwaters to achieve ground speeds often exceeding 50 km/h while extracting energy from the atmosphere rather than muscular power alone. Observations of species like the confirm that this adaptation enables non-stop journeys exceeding 10,000 km, such as trans-Pacific migrations, with minimal metabolic cost. Anatomically, shearwaters' long, narrow wings with high aspect ratios—ranging from about 8.4 in smaller species like the little shearwater to over 12 in larger ones like the great shearwater—optimize efficiency by reducing induced drag and enhancing lift-to-drag ratios during sustained soaring. These wings, combined with relatively low wing loadings of 0.3–0.6 g/cm² across procellariiform species, allow for stable, low-energy flight while supporting takeoff from water surfaces. Stiff tail feathers further aid in maintaining balance and control during sharp turns and low-altitude maneuvers in turbulent winds. To cope with intake during , shearwaters possess specialized nasal (supraorbital) salt glands that excrete hypertonic saline solutions, preventing osmotic stress and enabling prolonged marine flights without freshwater dependence. Olfactory navigation plays a critical role in shearwaters' ability to locate productive foraging areas and return to breeding colonies across vast expanses. These birds detect chemical signatures from upwelling zones, where nutrient-rich waters attract prey, guiding them to distant feeding grounds. Homing experiments with Manx shearwaters displaced hundreds of kilometers demonstrate that individuals with impaired olfaction (via chemical blockage) fail to orient directly homeward, instead following circuitous routes along coastlines and taking significantly longer to return, while controls and those with disrupted magnetic senses perform efficiently. Similar anosmia studies on Scopoli's shearwaters confirm that smell is essential for initial orientation, with affected birds showing reduced path efficiency (0.27 versus 0.56 for controls) before eventually homing via visual landmarks. Physiologically, shearwaters exhibit enhanced aerobic capacity in their flight muscles, characterized by high densities of oxidative enzymes and mitochondria that support prolonged through efficient fat metabolism rather than anaerobic bursts. This is vital for the intermittent required to initiate soaring cycles, with muscle fibers optimized for sustained low-intensity activity over days or weeks. Across species, values of 0.3–0.6 g/cm² provide a balance between structural strength for wave-riding takeoffs and aerodynamic efficiency for , underscoring the for transoceanic travel.

Taxonomy

Phylogeny

Shearwaters belong to the family within the order , which diverged from other lineages approximately 60 million years ago in the , with the crown group emerging around 40 million years ago during the Eocene. The fossil record of procellariiforms begins in the Eocene, but unambiguous shearwater fossils appear in the , exemplified by Diomedeoides brodkorbi, a stem-group procellariiform from the early () deposits in , indicating early diversification of tubenosed seabirds. records further document shearwater evolution, including a diminutive species akin to modern Calonectris from the Middle Calvert Formation in , suggesting the development of larger-bodied forms by the . These fossils highlight shearwaters' ancient origins as pelagic predators adapted to open oceans, with the family contributing the most species to the procellariiform record. Genomic studies in the 2020s, leveraging whole-genome sequencing and analyses, have resolved the phylogenetic relationships among shearwaters, confirming three main genera: Calonectris (larger Mediterranean species), Ardenna ( medium-to-large forms), and (predominantly small species). Traditional classifications rendered paraphyletic, as larger species now in Ardenna (e.g., A. puffinus) nested within it; this led to taxonomic revisions splitting Ardenna to achieve monophyly for . Hybridization events further complicate boundaries, such as between the critically endangered Balearic shearwater (Puffinus mauretanicus) and its sibling species the Yelkouan shearwater (Puffinus yelkouan), which has been shown to enhance survival in hybrid populations through adaptive . The reveals a basal divergence between the northern Calonectris and the southern Ardenna/ radiation, with the three genera splitting during the Middle Miocene around 15–10 million years ago, followed by accelerated speciation in the late driven by oceanographic shifts like intensified and cooling currents. Pleistocene glaciation episodes caused range contractions and local extinctions, particularly affecting northern and island populations, as evidenced by remains of extinct species like the Lava shearwater (Puffinus olsoni) from the , where post-glacial warming and sea-level rise contributed to biodiversity loss. These events underscore the role of climatic oscillations in shaping shearwater diversity. The 2024 update to the IOC World Bird List integrates these genomic insights, maintaining recognition of approximately 31 across the three genera while incorporating revisions such as elevating subspecies distinctions and renaming Audubon's shearwater to Sargasso shearwater (Puffinus lherminieri) based on phylogenetic evidence.

List of Species

Shearwaters comprise approximately 31 extant distributed across three genera within the family : Calonectris (four large, yellow-billed species primarily in the Atlantic and western Pacific), Ardenna (seven medium to large species with robust bills, mostly in southern oceans), and Puffinus (about 20 small to medium , often with more slender bills, widespread in tropical and temperate seas). This taxonomy reflects recent genomic studies that separated Ardenna from Puffinus based on phylogenetic divergence, with Calonectris forming a distinct . Extinct species, such as the Holocene-era Puffinus olsoni (lava shearwater, known from subfossil remains in the ), are included for completeness. Recent taxonomic revisions, including 2024 splits in the Puffinus lherminieri complex (e.g., recognizing distinct like the Galapagos shearwater P. subalaris), have refined species boundaries using genetic and morphological . Subspecies are noted where significant, particularly for population estimates and regional ; global populations are provided only for well-studied taxa.

Genus Calonectris

These species are characterized by their large size (40–56 cm), pale underparts, and breeding in subtropical to temperate islands, with foraging in offshore waters.
Binomial NameCommon NameIUCN StatusKey Identifiers (Size, Range)Notes
Calonectris borealisCory's ShearwaterLeast Concern45–56 cm; breeds on Macaronesian islands (Azores, Canaries, Madeira), ranges North AtlanticSplit from C. diomedea in 2024 based on vocal and genetic differences; global population ~500,000–1,000,000 breeding pairs.
Calonectris diomedeaScopoli's ShearwaterLeast Concern45–56 cm; breeds Mediterranean (e.g., Italy, Greece), ranges eastern Atlantic and MediterraneanRecognized as full species in 2024 split; subspecies include C. d. diomedea (mainland Europe) vs. C. d. alba (Libya); population ~300,000–500,000 breeding pairs.
Calonectris edwardsiiCape Verde ShearwaterNear Threatened43–49 cm; endemic breeder to Cape Verde Islands, ranges eastern AtlanticMonotypic; small population ~3,000–5,000 breeding pairs, vulnerable due to limited range.
Calonectris leucomelasStreaked ShearwaterNear Threatened48 cm; breeds Japan and Korea, ranges North PacificMonotypic; global population ~500,000 individuals, declining due to fishery bycatch.

Genus Ardenna

These species are larger (36–51 cm), often with dark plumage and white underwing patches, breeding in southern temperate to subantarctic regions and migrating northward.
Binomial NameCommon NameIUCN StatusKey Identifiers (Size, Range)Notes
Ardenna bulleriBuller's ShearwaterVulnerable36–42 cm; breeds New Zealand, ranges North PacificMonotypic; population ~50,000–100,000 breeding pairs, threatened by invasive predators.
Ardenna carneipesFlesh-footed ShearwaterNear Threatened43–46 cm; breeds Australia, New Zealand, ranges Pacific and Indian OceansMonotypic; global population >650,000 individuals, but declining from plastic ingestion.
Ardenna creatopusPink-footed ShearwaterVulnerable48 cm; breeds Chile (Juan Fernández Islands), ranges eastern PacificMonotypic; population ~2,000–4,000 breeding pairs, vulnerable to habitat loss.
Ardenna gravisGreat ShearwaterLeast Concern43–51 cm; breeds Tristan da Cunha (South Atlantic), ranges North AtlanticMonotypic; abundant, population ~10–20 million individuals.
Ardenna griseaSooty ShearwaterNear Threatened40–46 cm; breeds New Zealand, Australia, Chile, ranges northern hemisphereMonotypic; global population ~20 million, but declining from overharvesting.
Ardenna pacificusWedge-tailed ShearwaterLeast Concern41–46 cm; breeds tropical Pacific and Indian Oceans (e.g., Hawaii, Australia)Subspecies include dark and light morphs; population >1 million breeding pairs.
Ardenna tenuirostrisShort-tailed ShearwaterLeast Concern39–43 cm; breeds Tasmania and southern Australia, ranges North PacificMonotypic; population ~15–20 million, major migrant to Alaska.

Genus Puffinus

This diverse genus includes smaller species (20–38 cm), many with variable plumage, breeding on remote islands worldwide; recent splits have increased recognized diversity from ~15 to ~20 species.
Binomial NameCommon NameIUCN StatusKey Identifiers (Size, Range)Notes
Puffinus auricularisTownsend's ShearwaterEndangered30 cm; breeds Revillagigedo Islands (Mexico), ranges eastern PacificSubspecies P. a. auricularis; population <300 individuals, captive breeding ongoing.
Puffinus bailloniTropical ShearwaterLeast Concern26–29 cm; breeds tropical Indian and Pacific Oceans (e.g., Seychelles, Indonesia)Complex split in 2024; subspecies include P. b. dichrous (Christmas Island); population stable.
Puffinus baroliBarolo ShearwaterNear Threatened25–27 cm; breeds Macaronesia (Azores, Madeira, Canaries), ranges AtlanticSplit from Audubon's complex; subspecies P. b. baroli; population ~2,000–4,000 pairs.
Puffinus boydiBoyd's ShearwaterData Deficient25 cm; breeds New Zealand (possibly extinct on main islands)Subspecies of little shearwater; limited data, potential split.
Puffinus bryaniBryan's ShearwaterCritically Endangered26 cm; breeds possibly Midway Atoll (Hawaii), ranges PacificDescribed 2011 from subfossils; population unknown, presumed <50 individuals.
Puffinus bannermaniBannerman's ShearwaterVulnerable25 cm; breeds Solomon Islands, ranges western PacificMonotypic; population ~10,000 pairs, threatened by logging.
Puffinus elegansElegant ShearwaterLeast Concern28 cm; breeds Lord Howe Island (Australia), ranges South PacificRecently split; population ~20,000 pairs.
Puffinus gaviaFluttering ShearwaterLeast Concern23–25 cm; breeds Australia and New Zealand, ranges AustralasiaMonotypic; abundant, population >1 million.
Puffinus heinrothiHeinroth's ShearwaterVulnerable29 cm; breeds Solomon Islands, ranges western PacificMonotypic; population 250–999 individuals.
Puffinus huttoniHutton's ShearwaterEndangered36 cm; breeds New Zealand (South Island), ranges PacificMonotypic; population ~40,000 pairs, predation threats.
Puffinus lherminieriSargasso ShearwaterLeast Concern27–30 cm; breeds Caribbean, ranges western Atlantic2024 split limits to nominate form; subspecies formerly included others; population >100,000.
Puffinus mauretanicusBalearic ShearwaterCritically Endangered30–35 cm; breeds Balearic Islands (Spain), ranges western Mediterranean and AtlanticMonotypic; population ~3,000–7,000 mature individuals, severe decline.
Puffinus myrtaeRapa ShearwaterData Deficient25 cm; breeds Rapa Island (French Polynesia), ranges South PacificDescribed 2020; population unknown.
Puffinus nativitatisChristmas ShearwaterNear Threatened36 cm; breeds tropical Pacific (e.g., Hawaii, Line Islands), ranges central PacificSubspecies P. n. nativitatis and P. n. juana; population ~20,000–50,000.
Puffinus newelliNewell's ShearwaterEndangered30 cm; breeds Hawaiian Islands, ranges North PacificRevised in 2024 to include genetic confirmation as distinct; population ~10,000–20,000, light attraction threats.
Puffinus opisthomelasBlack-vented ShearwaterVulnerable30 cm; breeds Baja California (Mexico), ranges eastern PacificMonotypic; population ~10,000 pairs.
Puffinus persicusPersian ShearwaterLeast Concern32 cm; breeds Arabian Sea islands (e.g., Socotra), ranges Indian OceanMonotypic; population stable.
Puffinus puffinusManx ShearwaterLeast Concern30–35 cm; breeds northeast Atlantic (e.g., UK, Ireland), ranges AtlanticSubspecies P. p. puffinus (Atlantic); population >10 million.
Puffinus subalarisGalapagos ShearwaterVulnerable28 cm; breeds Galapagos Islands, ranges eastern PacificSplit from Audubon's in 2024; population ~10,000–20,000, invasive species threats.
Puffinus yelkouanYelkouan ShearwaterVulnerable30–35 cm; breeds central Mediterranean (e.g., Italy), ranges MediterraneanSplit from Manx; population ~12,000–15,000 pairs; P. y. yelkouan vs. Corsican subspecies.

Extinct Species

Puffinus olsoni (Lava Shearwater): Extinct (); ~30 cm, endemic to (Lanzarote, ); subfossil evidence indicates extinction post-human arrival ~2,000 years ago.

Behavior

Breeding

Shearwaters typically form long-term monogamous pair bonds, exhibiting high mate fidelity that enhances over multiple seasons. These pairs reunite annually at breeding colonies, where nocturnal displays occur to reaffirm bonds, involving distinctive calls such as cooing and moaning, along with mutual and duetting behaviors. Such displays are primarily conducted at night to minimize predation risk, with activity peaking during moonless periods. Breeding pairs construct nests in burrows or natural crevices on predator-free islands, selecting sites with suitable for excavation or rocky shelters for . Each pair lays a single white per season, with incubation shared equally between both parents and lasting 45 to 65 days, depending on ; for instance, in the wedge-tailed shearwater (Ardenna pacifica), it averages 52 to 53 days. During incubation shifts, one parent remains on the while the other forages at sea, with no feeding occurring during these extended stints. Chicks hatch after the incubation period and are brooded continuously by parents for the first few days before receiving regurgitated meals. involves alternating short trips for chick provisioning and longer trips for self-maintenance, with both adults delivering energy-rich stomach oil derived from digested prey , which supports rapid chick growth. Chick development to fledging spans 60 to 100 days, during which nestlings gain significant mass—often doubling adult weight—before departing independently; in the (Ardenna tenuirostris), this period extends up to 100 days, culminating in a phase post-parental departure. In some populations, human activities intersect with chick-rearing; for example, the chicks are harvested during the traditional season in , , where approximately 200,000 fledglings are collected annually for their oil, flesh, and feathers under regulated quotas. Breeding seasonality varies by hemisphere: southern species, such as the , initiate activities from October to March, aligning with austral summer, while northern species like the (Puffinus puffinus) breed from June to September. Overall reproductive success rates range from 60% to 80%, largely limited by predation on eggs and chicks by introduced mammals like rats, which can halve fledging rates in affected colonies.

Feeding

Shearwaters primarily feed on small schooling such as anchovies and sardines, cephalopods including , and crustaceans like and . These species opportunistically scavenge fishery discards and offal, particularly damaged , which supplements their diet during breeding seasons near human activity. To provide energy-dense nourishment for chicks, adult shearwaters process ingested prey in their proventriculus to produce stomach oil, a lipid-rich substance derived from partial of and . Foraging strategies vary by species and conditions but typically involve surface-seizing or pattering to capture prey while skimming the water, often in flocks over nutrient-rich zones where prey aggregates. Many species pursue prey through underwater dives, propelling themselves with partially opened wings in a motion rather than foot paddling, reaching depths of 5–20 m on average but up to 66 m in wedge-tailed shearwaters. Flock feeding enhances efficiency in these dynamic areas, with birds coordinating to exploit ephemeral prey patches. Adults maintain high intake rates to support their energetically demanding lifestyle, feeding every 4–10 minutes during prolonged flights as inferred from patterns in streaked shearwaters, which average five events per hour and equate to excreting about 30 g hourly. Daily consumption typically ranges from 10–20% of body mass, varying with prey energy content and breeding demands. Physiological adaptations facilitate prey detection and capture, including tubular nostrils that enable olfaction of volatile oily compounds like emanating from planktonic prey aggregations. Species such as the exemplify deep-diving capabilities, routinely accessing mesopelagic layers up to 50 m or more to target vertically migrating and fish during nocturnal foraging.

Movements

Shearwaters are renowned for their extraordinary long-distance migrations, which enable them to exploit productive oceanic regions seasonally. The sooty shearwater (Ardenna grisea) undertakes one of the most extensive annual circuits documented among birds, traveling approximately 64,000 km in a figure-eight pattern across the Pacific Ocean, from breeding colonies in New Zealand and Alaska to wintering grounds off South America and back. Similarly, the Manx shearwater (Puffinus puffinus) follows a transatlantic route of about 15,500 km round-trip, migrating from breeding sites in the North Atlantic, such as the British Isles, to wintering areas along the Patagonian Shelf off Argentina, with the northward journey passing through the eastern Caribbean. These migrations, tracked via satellite and geolocators in studies from the 2000s through the 2020s, highlight how shearwaters connect distant hemispheres, often covering over 1,000 km per day under optimal conditions. Navigation during these journeys relies on a combination of environmental cues, with olfactory maps playing a primary role in species like (Calonectris diomedea). Experimental displacements and tests have shown that shearwaters use odors, such as from , to orient over open oceans, often homing successfully even when magnetic cues are disrupted. Geomagnetic fields provide directional and positional information, particularly for juveniles; for instance, Manx shearwater chicks extrapolate magnetic gradients to guide their initial southward flights beyond familiar ranges. , including sun and star compasses, may supplement these in some contexts, though olfactory and magnetic mechanisms dominate in pelagic environments, as evidenced by tracking data revealing efficient, wind-assisted paths. After fledging, juvenile shearwaters enter a prolonged pelagic dispersal phase, wandering widely across oceans for 3–5 years before returning to prospective breeding sites, a that allows maturation away from pressures. This extended non-breeding period is supported by their exceptional longevity, with individuals like the reaching over 50 years, enabling dozens of repeated migrations over a lifetime. Seasonally, migrations are timed to breeding cycles: adults arrive at colonies in pre-breeding periods from late winter to spring for courtship and egg-laying, followed by a post-breeding exodus in late summer or autumn after chick fledging, with routes influenced by that facilitate tailwind-assisted travel and reduce energy costs. For example, sooty shearwaters exploit global wind circulation and the Coriolis effect to loop efficiently between hemispheres.

Habitat and Distribution

Breeding Sites

Shearwaters primarily establish breeding colonies on remote oceanic islands that are free from mammalian predators, providing safe environments for nesting in burrows. These sites are typically located in temperate to subtropical regions across the Atlantic, Pacific, and Southern Oceans, where the birds excavate nests in , tussock grasslands, or cliff crevices to protect eggs and chicks from avian predators and harsh weather. Key breeding locations include the archipelago in the South Atlantic, which hosts large colonies of great shearwaters (Ardenna gravis) on Nightingale, Inaccessible, and Gough Islands, with millions of pairs nesting in burrows amid tussock vegetation. In the North Atlantic, the of serve as the exclusive breeding grounds for Balearic shearwaters (Puffinus mauretanicus), utilizing coastal cliffs and caves such as Sa Cella on , supporting approximately 2,000 breeding pairs as of 2021. Pacific examples feature the , where wedge-tailed shearwaters (Ardenna pacifica) and Newell's shearwaters (Puffinus newelli) nest in burrows under sand dunes and soil on islands like Kauai, , and Molokai, with colonies spanning low-elevation coastal areas. Further south, the off are a major site for sooty shearwaters (Ardenna grisea), accommodating millions of pairs in dense burrows beneath Olearia forest and tussock grass. In the , Island off holds one of the world's largest (Puffinus puffinus) colonies, estimated at 350,000 pairs burrowed into grassy slopes (as of 2025). Colony densities vary by species and habitat but can reach up to 1,000 pairs per in optimal conditions, as observed in some wedge-tailed shearwater sites where burrows cluster in friable soils for efficient excavation. Site selection is influenced by factors such as proximity to productive grounds to minimize energy expenditure during chick-rearing, exposure to that facilitate takeoff from steep slopes or cliffs, and dense vegetation cover that conceals burrows from predators. These preferences ensure high breeding success, though historical human activities like extraction on some islands have altered and prompted localized shifts in colony distribution. Global hotspots for shearwater breeding encompass the North Atlantic's Balearic archipelago, sub-Antarctic islands in the such as the Snares and groups, and Pacific archipelagos like and New Zealand's offshore islets, collectively supporting diverse in predator-free isolation.

Foraging Areas

Shearwaters primarily in pelagic habitats characterized by high productivity, such as open ocean , continental shelves, and convergence zones where nutrient-rich waters support abundant prey. For instance, the black-vented shearwater ( opisthomelas) targets zones along the within the system, exploiting localized areas of enhanced . Similarly, the Cape Verde shearwater (Calonectris edwardsii) extensively in the Large Marine Ecosystem off , a region of persistent that sustains dense aggregations of small and crustaceans. These habitats provide the dynamic oceanographic conditions essential for shearwater success. Shearwaters typically hunt from the surface to depths of up to 90 meters in temperate and subtropical waters, though most dives are shallow (less than 20 meters), while generally avoiding polar extremes due to unsuitable thermal regimes and prey availability. Species like the great shearwater (Ardenna gravis) exhibit flexible diving , with most occurring in the upper 20 meters and dives rarely exceeding 20 meters. In the Mediterranean, (Calonectris diomedea) concentrates efforts in nutrient-rich straits and shelf waters, such as those off the eastern , where depths remain below 200 meters and supports consistent food resources. This depth preference aligns with the distribution of their primary prey, including and squid, in these warmer oceanic realms. Foraging ranges of shearwaters often overlap with those of albatrosses in shared productive zones, promoting sympatric exploitation of resources without significant competition due to differing foraging techniques. For example, in the North Pacific, Laysan albatrosses (Phoebastria immutabilis) and shearwaters co-occur over subtropical convergence areas, where both target epipelagic prey but albatrosses favor surface scavenging while shearwaters pursue diving schools. Shearwaters also exhibit seasonal shifts in foraging distribution to track prey migrations, such as krill blooms in the , allowing species like the (Ardenna tenuirostris) to follow euphausiid concentrations from sub-Antarctic fronts northward into temperate waters. These adjustments ensure access to ephemeral high-density food patches. Shearwaters show strong environmental dependencies on oceanographic features like s and fronts, which aggregate prey and can be monitored via satellite remote sensing for predicting foraging hotspots. Balearic shearwaters ( mauretanicus), for instance, repeatedly target -enriched fronts along the Catalan , where disruptions enhance nutrient and blooms. Such reliance on these detectable structures underscores the role of fine-scale ocean dynamics in shaping shearwater ecological niches across pelagic environments.

Conservation

Threats

Shearwaters face significant threats from in commercial fisheries, particularly through entanglement in longlines and gillnets, as well as collisions with trawl nets. Globally, longline fisheries are estimated to kill between 160,000 and 320,000 seabirds annually, with shearwaters comprising a substantial portion due to their attraction to baited hooks during . For instance, sooty shearwaters (Ardenna grisea) experience high rates in these operations, contributing to population declines in regions like the North Pacific and . Pre-mitigation estimates in trawl fisheries indicated hundreds of sooty shearwaters captured per year, though exact global figures for trawls remain underreported but significant for species like the flesh-footed shearwater (Ardenna carneipes). Invasive species pose a major risk to shearwater breeding colonies on islands, where introduced predators such as rats and feral cats prey heavily on eggs, chicks, and adults. Black rats () and ship rats () have decimated populations by raiding burrows, with studies on islands like the Falklands and showing predation rates that can reduce fledging success by over 50% in affected sites. Feral cats exacerbate this by targeting ground-nesting species, such as streaked shearwaters (Calonectris leucomelas) on Japanese islands, where seasonal diet shifts from rats to seabirds lead to direct mortality. Habitat loss compounds these issues through caused by from introduced ungulates like goats and sheep, which degrade burrowing substrates; for example, on , has eroded up to 50% of pink-footed shearwater (Ardenna creatopus) nesting areas. Additionally, ingestion is rampant, with 2020s necropsies revealing in approximately 90% of flesh-footed shearwater fledglings on and Cory's shearwaters (Calonectris borealis) in the Mediterranean, leading to reduced growth and internal damage. Climate change intensifies threats to shearwaters by altering ocean conditions and increasing extreme weather events. Ocean warming shifts prey distributions, such as krill and fish, forcing shearwaters to forage farther or on lower-quality food, as observed in sooty shearwaters experiencing nutritional stress in the warming North Pacific. Increased storm frequency disrupts breeding; for instance, in 2023 devastated colonies, causing burrow flooding and chick mortality in species like the fluttering shearwater ( gavia), with similar risks projected for 2024 events amid rising cyclone intensity. Other threats include , which disorients fledglings during their first flights, attracting them to coastal lights and resulting in grounding and predation; wedge-tailed shearwaters (Ardenna pacifica) in suffer thousands of such "fallouts" annually. Historical hunting, known as , targeted chicks in but is now regulated through customary practices limited to specific islands and seasons to ensure sustainability. Many shearwater species, such as the Newell's shearwater (Puffinus newelli), are listed as vulnerable or endangered by the IUCN due to these cumulative pressures.

Conservation Efforts

Conservation efforts for shearwaters have focused on habitat restoration, particularly through the eradication of invasive species on breeding islands, which has led to significant population recoveries in several cases. For instance, on the Isles of Scilly in the UK, the removal of invasive rats from St Agnes and Gugh islands resulted in a rapid increase in Manx shearwater (Puffinus puffinus) breeding pairs, from 22 recorded in 2013 to over 200 by 2023, demonstrating the effectiveness of such interventions in restoring seabird colonies. Similarly, on Lehua Island in Hawaii, the successful eradication of rats in 2021 has protected wedge-tailed shearwater (Ardenna pacifica) nesting sites, preventing predation and allowing for anticipated population growth in this key Pacific breeding ground. These restoration projects, often led by organizations like Island Conservation and local wildlife trusts, highlight how targeted invasive species management can reverse declines within a decade. International agreements and fisheries regulations have played a crucial role in mitigating , a major threat to migratory shearwaters. The Agreement on the Conservation of Albatrosses and Petrels (ACAP), established in 2006, promotes measures such as bird-scaring lines (also known as streamer or tori lines) and weighted branch lines to reduce interactions with longline fisheries; these tools have been shown to decrease bycatch rates by 88-100% when properly deployed, including in the South Atlantic where shearwaters like the great shearwater (Ardenna gravis) forage. ACAP's action plans, adopted by over 25 member countries, mandate the integration of these mitigation devices in fishing operations and facilitate to refine protections for listed shearwater species. In regions like the Pacific and Atlantic, compliance with ACAP guidelines has contributed to stabilized populations for several species by curbing incidental mortality. Ongoing monitoring and research initiatives, including advanced tracking technologies, support targeted conservation actions. The Mediterranean Commission (CIESM) has deployed GPS-GSM transmitters on Yelkouan shearwaters ( yelkouan) since the early 2020s, providing real-time interactive migration maps that reveal routes and high-risk areas, enabling better protection during non-breeding periods. Complementing this, campaigns to reduce [plastic pollution](/page/plastic pollution)—such as the European Union's SeaBiL project—aim to curb ingestion by seabirds, including Cory's shearwater (Calonectris borealis), through source reduction and beach cleanups, as plastics have been found in over 90% of examined individuals in some colonies. Reintroduction efforts for endangered , like the Newell's shearwater ( newelli), involve translocating fledglings to predator-free sites on Kauai, , with high survival rates exceeding 97% post-release, fostering new breeding populations. These combined efforts have yielded notable population recoveries and informed global assessments. In the UK, protected areas have supported a rebound in Manx shearwater numbers, with colonies on Lundy Island showing spectacular growth from near absence in the 1980s to thousands of pairs by the 2020s, attributed to habitat safeguards and invasive control. As of the 2025 IUCN Red List assessments, more than 20 shearwater species are classified as Vulnerable or higher threat levels, but stable or improving trends are evident for several, such as the sooty shearwater (Ardenna grisea), due to these interventions, underscoring the potential for broader recovery with sustained international cooperation.

References

  1. https://www.merriam-webster.com/dictionary/shearwater
  2. http://mars.unh.edu/wild/forthebirdsprocellariidae.asp
  3. https://www.seabirdtracking.org/species/large-petrels-and-shearwaters/
  4. https://birdsoftheworld.org/bow/species/procel3/cur/introduction
  5. https://www.allaboutbirds.org/guide/Great_Shearwater/overview
  6. https://datazone.birdlife.org/species/factsheet/short-tailed-shearwater-ardenna-tenuirostris
  7. https://datazone.birdlife.org/species/factsheet/newells-shearwater-puffinus-newelli
  8. https://datazone.birdlife.org/species/factsheet/balearic-shearwater-puffinus-mauretanicus
  9. https://www.allaboutbirds.org/guide/Great_Shearwater/id
  10. https://www.oiseaux.net/maps/little.shearwater.html
  11. https://www.vogelwarte.ch/en/birds-of-switzerland/cory-s-shearwater/
  12. https://animaldiversity.org/accounts/Calonectris_diomedea/
  13. https://doi.org/10.2173/bow.procel3.01
  14. https://www.allaboutbirds.org/guide/Sooty_Shearwater/id
  15. https://www.rspb.org.uk/birds-and-wildlife/manx-shearwater
  16. https://app.birda.org/species-guide/7523/Manx_Shearwater
  17. https://pmc.ncbi.nlm.nih.gov/articles/PMC4987799/
  18. https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=8949&context=wilson_bulletin
  19. https://www.ahajournals.org/doi/10.1161/01.CIR.21.5.955
  20. https://royalsocietypublishing.org/doi/10.1098/rstb.1993.0079
  21. https://www.nature.com/articles/s41598-017-09738-5
  22. https://www.nature.com/articles/srep16486
  23. https://journals.biologists.com/jeb/article/214/15/2455/10417/Elevated-performance-the-unique-physiology-of
  24. https://www.bird-phylogeny.de/superorders/aequornithes/procellariiformes/
  25. https://bioone.org/journals/acta-palaeontologica-polonica/volume-55/issue-1/app.2009.0069/New-Skeleton-from-the-Early-Oligocene-of-Germany-Indicates-a/10.4202/app.2009.0069.full
  26. https://meridian.allenpress.com/pbsw/article/122/4/466/37543/A-new-diminutive-species-of-shearwater-of-the
  27. https://www.mdpi.com/2673-6500/4/2/12
  28. https://onlinelibrary.wiley.com/doi/10.1111/jbi.14291
  29. https://phys.org/news/2025-09-hybridization-boosts-survival-europe-threatened.html
  30. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0016072
  31. https://www.worldbirdnames.org/new/updates/english-names/
  32. https://pmc.ncbi.nlm.nih.gov/articles/PMC3013140/
  33. https://science.ebird.org/en/use-ebird-data/the-ebird-taxonomy/2024-ebird-taxonomy-update
  34. https://datazone.birdlife.org/species/factsheet/scopolis-shearwater-calonectris-diomedea
  35. https://datazone.birdlife.org/species/factsheet/streaked-shearwater-calonectris-leucomelas
  36. https://datazone.birdlife.org/species/factsheet/bullers-shearwater-ardenna-bulleri
  37. https://datazone.birdlife.org/species/factsheet/flesh-footed-shearwater-ardenna-carneipes
  38. https://datazone.birdlife.org/species/factsheet/great-shearwater-ardenna-gravis
  39. https://datazone.birdlife.org/species/factsheet/sooty-shearwater-ardenna-grisea
  40. https://datazone.birdlife.org/species/factsheet/wedge-tailed-shearwater-ardenna-pacifica
  41. https://www.birdpop.org/docs/pubs/Pyle_et_al_2011_A_New_Species_of_Shearwater_from_Midway_Bryans_Shearwater.pdf
  42. https://datazone.birdlife.org/species/factsheet/huttons-shearwater-puffinus-huttoni
  43. https://escholarship.org/content/qt01k3q8ms/qt01k3q8ms.pdf
  44. http://www.pelagicos.net/MARS4040_6040/references/Whittow_1997.pdf
  45. https://birdsoftheworld.org/bow/species/manshe/cur/sounds
  46. https://nre.tas.gov.au/wildlife-management/fauna-of-tasmania/birds/complete-list-of-tasmanian-birds/short-tailed-shearwater
  47. https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=23110&context=auk
  48. https://birdsoftheworld.org/bow/species/wetshe/cur/foodhabits
  49. https://link.springer.com/article/10.1007/s00227-021-03994-w
  50. https://www.mdpi.com/2076-2615/12/9/1069
  51. https://birdsoftheworld.org/bow/species/manshe/cur/foodhabits
  52. https://www.researchgate.net/publication/335657168_Diving_Depths_of_Shearwaters
  53. https://www.sciencenews.org/article/streaked-shearwaters-poop-flying
  54. https://www.int-res.com/articles/meps/167/m167p261.pdf
  55. https://journals.biologists.com/jeb/article/211/11/1706/9495/Sensory-ecology-on-the-high-seas-the-odor-world-of
  56. https://pmc.ncbi.nlm.nih.gov/articles/PMC2881033/
  57. https://www.pnas.org/doi/10.1073/pnas.0603715103
  58. https://pmc.ncbi.nlm.nih.gov/articles/PMC2660961/
  59. https://onlinelibrary.wiley.com/doi/10.1111/geb.70004
  60. https://journals.biologists.com/jeb/article/216/15/2798/11490/Oceanic-navigation-in-Cory-s-shearwaters-evidence
  61. https://www.sciencedirect.com/science/article/pii/S0960982221001160
  62. https://www.bto.org/learn/about-birds/birdfacts/manx-shearwater
  63. https://www.nature.com/articles/s41598-018-21608-2
  64. https://www.audubon.org/field-guide/bird/corys-shearwater
  65. https://birdsoftheworld.org/bow/species/balshe1/cur/introduction
  66. https://www.acap.aq/news/news-archive/60-2013-news-archive/1300-acap-breeding-sites-no-3-sa-cella-sa-dragonera-mallorca-balearic-islands-home-of-the-balearic-shearwater
  67. https://hbs.bishopmuseum.org/birds/rlp-monograph/pdfs/02-Galliformes-Procellariiformes/WTSH.pdf
  68. https://newsroom.pembrokeshire.gov.uk/news/volunteers-mobilise-to-rescue-stranded-manx-shearwaters-across-pembrokeshire
  69. http://www.marineornithology.org/PDF/30_1/30_1_3.pdf
  70. https://pmc.ncbi.nlm.nih.gov/articles/PMC9045628/
  71. https://www.welshwildlife.org/visit/skomer-island
  72. https://birdsoftheworld.org/bow/species/bkvshe/cur/introduction
  73. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0139390
  74. https://www.researchgate.net/publication/268243075_Maximum_dive_depths_of_eight_New_Zealand_Procellariiformes_including_Pterodroma_species
  75. https://pmc.ncbi.nlm.nih.gov/articles/PMC2994869/
  76. https://esajournals.onlinelibrary.wiley.com/doi/10.1890/1051-0761%25282006%2529016%255B1683%253AOHOAEM%255D2.0.CO%253B2
  77. https://movementecologyjournal.biomedcentral.com/articles/10.1186/s40462-015-0063-4
  78. https://www.sciencedirect.com/science/article/pii/S0006320715002074
  79. https://www.int-res.com/articles/theme/m391p183.pdf
  80. https://www.ios-wildlifetrust.org.uk/our-projects/isles-scilly-seabird-recovery-project
  81. https://dlnr.hawaii.gov/blog/2021/04/21/nr21-076/
  82. https://www.acap.aq/about-acap
  83. https://wsg.washington.edu/wordpress/wp-content/uploads/publications/Streamer-Lines-Reduce-Seabird-Bycatch-Longliners.pdf
  84. https://ciesm.org/our-science/programs/seabirds/tracking-migration/interactive-map-2025/
  85. https://cinea.ec.europa.eu/news-events/news/protecting-europes-seabirds-tackling-plastic-pollution-life-2024-09-03_en
  86. https://www.frontiersin.org/journals/conservation-science/articles/10.3389/fcosc.2023.1177789/full
  87. https://insideecology.com/2023/10/12/shear-success-for-lundys-seabirds-thanks-to-decades-of-conservation-effort/
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