Arctic Tern

For the aircraft, see Arctic Aircraft Arctic Tern . For the racehorse, see Arctic Tern (horse) .

Arctic Tern

Flatey Island, Western Iceland

Conservation status

Least Concern  (IUCN 3.1 ) [1]

Scientific classification

Kingdom: Animalia Phylum: Chordata Class: Aves Order: Charadriiformes Family: Laridae Genus: Sterna Species: S. paradisaea

Binomial name

Sterna paradisaea Pontoppidan , 1763 [2]

Range of S. paradisaea   Breeding grounds •   wintering grounds •   migration routes

Synonyms

Sterna portlandica Sterna pikei

The Arctic tern (Sterna paradisaea) is a rather unremarkable-looking tern within the Laridae family , if one were to judge solely by its plumage. However, its true distinction lies not in its appearance, but in its almost absurd dedication to global travel. This particular bird claims a circumpolar breeding range that stretches across the Arctic and sub-Arctic expanses of Europe—venturing as far south as the rugged coasts of Brittany —Asia, and North America , reaching down to the rather more hospitable shores of Massachusetts .

What truly sets this species apart, making it a living, feathered testament to sheer endurance, is its profoundly migratory nature. The Arctic tern essentially experiences two summers every single year, embarking on a convoluted, mind-boggling journey from its chilly northern breeding grounds all the way to the frozen Antarctic coast for the southern summer, only to turn around and repeat the entire arduous process approximately six months later. Recent, more precise studies have unveiled average annual round-trip distances that would make lesser creatures weep with exhaustion: roughly 70,900 km (38,300 nmi) for individuals nesting in the glacial landscapes of Iceland and Greenland , and a slightly less insane, but still formidable, 48,700 km (26,300 nmi) for those starting their journey from the Netherlands . And then there’s the overachiever: one particular individual from the Farne Islands in Northumberland, equipped with a light level geolocator tag, managed to cover an utterly staggering 96,000 km (52,000 nmi) in a mere ten months, from the conclusion of one breeding season to the dawn of the next. These distances, to be clear, are not merely impressive; they represent, by a considerable margin, the longest migrations documented in the entire animal kingdom.

Arctic terns are classified as medium-sized birds, though their ambition far outstrips their physical dimensions. They typically measure between 28–39 cm (11–15 in) in length and boast a wingspan of 65–77 cm (26–30 in) [3] [4], all while weighing in at a rather modest average of around 100 g [5]. During their breeding season, their plumage presents a relatively understated palette of grey and white, accented by a strikingly blood-red beak and matching feet. A sharp black crown and nape contrast with crisp white cheeks, giving them an air of perpetual alertness. The mantle is a clean grey, with the scapulars also grey, delicately tipped with white. Their upper wings exhibit a similar grey, featuring a distinct white leading edge and a subtle, narrow blackish trailing edge along the primary feathers. The collar is unblemished white, as is the rump. Their deeply forked tail, a characteristic feature of many terns, is whitish with grey outer webs. Come winter, a slight shift occurs: the forehead acquires a partial white hue, and their vibrant red bill and legs darken to black [3]. Juveniles, still finding their way in the world, also display a partly white forehead and possess narrow, pale orangey-brown fringes on their grey mantle feathers—a detail that distinguishes them from the common tern , whose mantle feathers tend to be more uniformly gingery-brown [3].

These birds are also remarkably long-lived, with many individuals routinely reaching ages of fifteen to thirty years, and one particularly tenacious specimen holding the record at 31 years [5]. Their diet primarily consists of fish and various small marine invertebrates . Despite the immense distances they traverse and the challenges they face, the species remains abundant, with an estimated global population of two million individuals. While the overall trend in their population numbers isn’t entirely clear, historical exploitation has regrettably led to significant reductions in their numbers, particularly in the more accessible southern reaches of their vast range.

Etymology

The genus name, Sterna, is rather uncreatively derived from the Old English word “stearn,” which, as you might have guessed, simply means “tern” [6]. One might expect a bit more flair for a creature that defies all logical limits of travel, but alas. The specific epithet, paradisaea, hails from Late Latin paradisus, meaning “paradise” [7]. Perhaps a nod to the two summers it enjoys, or simply a poetic flourish by someone who hadn’t yet seen the bleakness of the Antarctic.

The Scots names pictarnie [8], tarrock [9], and their numerous variations, are widely believed to be onomatopoeic , echoing the bird’s distinctive call [10]. Due to the persistent inability of some to differentiate between the Arctic tern and its close relative, the common tern , all these informal common names are, rather lazily, shared between the two [11]. Because why make things easy, right?

Distribution and migration

An Arctic tern nesting on the Farne Islands , from where the longest migration is recorded

The Arctic tern boasts a continuous, truly global circumpolar breeding distribution, a testament to its widespread adaptability. There are, refreshingly, no accepted subspecies , simplifying matters for those of us who prefer not to split hairs unnecessarily. During the northern summer, these birds can be found diligently nesting in coastal regions across the cooler temperate zones of North America and Eurasia . Then, as the seasons dictate, they depart, spending the southern summer at sea, ranging all the way to the frigid northern edge of the Antarctic ice [12].

This species is, of course, legendary for its migration; it undertakes an annual, epic flight from its Arctic breeding grounds to the Antarctic and back again. The most direct path between these two extreme poles is a mere 19,000 km (12,000 mi), but as we’ll see, these birds rarely take the direct path. This extraordinary journey ensures that the Arctic tern experiences two summers each year, basking in more daylight than any other creature on this planet [13]. Imagine the perpetual tan.

One particularly striking illustration of this bird’s astonishing long-distance flying prowess involves an Arctic tern that was ringed as an unfledged chick on the Farne Islands , Northumberland , UK, during the northern summer of 1982. This fledgling, barely out of the nest, managed to reach Melbourne , Australia, by October—a mere three months after fledging—covering a staggering distance of over 22,000 km (14,000 mi) [14]. Another equally impressive feat involved a chick ringed in Labrador , Canada , on July 23, 1928, which was subsequently discovered in South Africa just four months later [15]. Clearly, these birds are not to be underestimated.

A comprehensive 2010 study, employing tracking devices affixed to the birds, confirmed that these anecdotal examples are far from anomalous for the species . In fact, the research shockingly revealed that previous estimates had gravely underestimated the true annual distances traversed by the Arctic tern . Eleven birds, specifically those breeding in Greenland or Iceland , were found to cover an average of 70,900 km (38,300 nmi) within a single year, with one exceptional individual logging a maximum of 81,600 km (44,100 nmi) [16]. The significant discrepancy from earlier estimations is attributed to the birds adopting meandering, rather than straight, courses, a strategic deviation from what was previously assumed. These intelligent aviators follow a somewhat convoluted route, not out of indecision, but to judiciously exploit prevailing winds, optimizing their energy expenditure across vast oceanic stretches [17]. Considering the average Arctic tern lives for approximately 30 years, and based on the findings of this research, an individual will accumulate an astonishing travel distance of some 2.4 million km (1.5 million mi) over its lifetime. For context, that’s the equivalent of making a roundtrip from Earth to the Moon more than three times over [18]. Your commute suddenly seems less daunting, doesn’t it?

A subsequent 2013 tracking study, focusing on half a dozen Arctic terns that breed in the Netherlands [19], reported average annual migration distances of approximately 48,700 km (26,300 nmi). On their southbound journey, these particular birds largely adhered to the coastlines of Europe and Africa [20], perhaps favoring familiar landmarks over the vast, open ocean.

The record, however, was shattered by a 2015–2017 study tracking Arctic terns from the Farne Islands in Northumberland. An individual, identifiable by its light level geolocator tag ‘G82’, achieved a truly mind-boggling 96,000 km (52,000 nmi) in just 10 months. This wasn’t merely the length of the Atlantic Ocean or the breadth of the Indian Ocean ; this bird traversed half the South Pacific to the boundary between the Ross and Amundsen Seas , before deciding to return west along the Antarctic coast and back up the Atlantic [21] [22] [23]. It’s almost as if it was trying to prove a point.

Given the sheer scale of their oceanic travels, it should come as no surprise that Arctic terns typically migrate sufficiently far offshore that sightings from land outside the breeding season are, frankly, quite rare [24]. They have better things to do than pose for your binoculars.

Description and taxonomy

The Arctic tern is a medium-sized avian marvel, measuring approximately 33–36 cm (13–14 in) from the very tip of its beak to the end of its deeply forked tail. Its impressive wingspan stretches to 76–85 cm (30–33 in) [24], allowing for those incredible migrations. Despite these dimensions, its weight remains a relatively light 86–127 g (3.0–4.5 oz). The beak is a distinctive dark red, complemented by equally short, dark red legs and practical webbed feet. Like the majority of terns, the Arctic tern possesses high aspect ratio wings —designed for efficient, long-distance flight—and that characteristic deeply forked tail, which aids in aerial maneuverability [24].

The adult plumage is predominantly grey on its upper surfaces, with a sharply defined black nape and crown, sharply contrasting with immaculate white cheeks. The upperwings are a pale grey, with a unique translucent quality near the wingtip, a subtle detail that distinguishes it in flight. The tail is pure white, and the underparts are a delicate pale grey. Both sexes are remarkably similar in appearance, suggesting that in their world, utility trumps flamboyant sexual dimorphism. The winter plumage is largely consistent, though the crown becomes notably whiter and the bill darkens further [24].

Juveniles present a slightly different picture: their bills and legs are black, their wings have a “scaly” appearance, and their mantle feathers are tipped with dark markings. They also exhibit a dark carpal wing bar and shorter tail streamers [24]. During their inaugural summer, these young birds also display a whiter forecrown [25].

The species possesses a repertoire of calls , the two most frequently heard being the alarm call—issued with urgent intensity when potential predators, such as humans or other large mammals , trespass into their colonies—and the advertising call [26].

While the Arctic tern shares a superficial resemblance with the common and roseate terns , a keen observer will note subtle differences in its colouring, flight profile, and vocalizations. Compared to the common tern , the Arctic tern sports a longer tail and a uniformly coloured bill, lacking the dark tip often seen in its common counterpart. The primary distinctions from the roseate tern lie in its slightly darker grey plumage and perceptibly longer wings [27]. Aurally, the Arctic tern’s call is distinctly more nasal and rasping than that of the common tern , and it is effortlessly distinguishable from the softer calls of the roseate tern [27].

This bird’s closest evolutionary kin are found among a group of South Polar species : the South American (Sterna hirundinacea), Kerguelen (S. virgata), and Antarctic (S. vittata) terns [28]. A testament to the global reach of this avian lineage.

It’s worth noting, for those with a penchant for historical taxonomic quirks, that the immature plumages of the Arctic tern were, at one point, mistakenly described as entirely separate species , grandly named Sterna portlandica and Sterna pikei [29]. A classic case of overthinking, perhaps.

Reproduction

Breeding for the Arctic tern typically commences around its third or fourth year of life [30]. These birds are staunchly monogamous, generally mating for life, and in the vast majority of cases, they exhibit a remarkable fidelity to their chosen colony, returning to the same site year after year [31]. Courtship is an elaborate, almost theatrical affair, particularly for those birds embarking on their first nesting season [32].

The ritual often begins with a display known as the “high flight,” where the female initiates a chase, pursuing the male to considerable altitudes before they both gracefully descend in a synchronized, slow glide. This aerial ballet is subsequently followed by “fish flights,” during which the male presents the female with offerings of fish, a practical demonstration of his foraging prowess and commitment. Ground-based courtship involves a series of distinctive struts, with the male holding his tail raised and wings slightly lowered, a subtle, perhaps slightly awkward, dance. Following these displays, both birds will typically take to the air again, circling each other in a final, reciprocal affirmation [32].

Once the initial courtship is complete, both sexes collaboratively agree upon a suitable nest site, and both will fiercely defend this chosen territory. Throughout this period, the male diligently continues to provide the female with food, reinforcing their bond. Mating itself occurs shortly after this collaborative nest selection [32]. Breeding activities unfold in colonies , typically situated on coastal margins, isolated islands, and occasionally venturing inland onto tundra landscapes in close proximity to water bodies. The Arctic tern frequently forms mixed flocks with the common tern during these breeding periods. Each clutch usually comprises one to three eggs , with two eggs being the most common number [24].

This species is renowned as one of the most aggressive terns, exhibiting an almost fanatical defensiveness of its nest and young. It will not hesitate to launch direct, fearless attacks on perceived threats, including humans and larger predators, typically aiming for the top or back of the head. While its modest size means it cannot inflict serious injury on an animal of human proportions, it is perfectly capable of drawing blood and is remarkably effective at repelling a diverse array of raptorial birds, formidable polar bears [33], and smaller mammalian predators such as foxes and cats [13]. A creature this small, yet so utterly without fear, is truly something to behold.

The nest itself is typically a simple depression scraped into the ground, which may or may not be minimally lined with sparse bits of grass or other readily available materials. The eggs are mottled and expertly camouflaged, a crucial defense against predators. Both sexes share the demanding duties of incubation, with the young chicks hatching after a period of 22–27 days and subsequently fledging —developing their flight feathers and becoming capable of flight—after 21–24 days [24]. Should the parents be frequently disturbed and forced to flush from the nest, the incubation period can, under stress, extend to as long as 34 days [26].

Upon hatching, the chicks emerge covered in soft downy feathers. Being precocial , meaning they are relatively mature and mobile at birth, the chicks begin to move around and tentatively explore their immediate surroundings within one to three days post-hatching [34]. They generally do not stray far from the safety of the nest. For the first ten days after hatching, the chicks are diligently brooded by the adults, who provide essential warmth and protection [35]. Both parents are equally committed to caring for their hatchlings [24]. The diet of the chicks consistently includes fish, and notably, the parents demonstrate a selective foraging strategy, consistently bringing larger prey items back to their young than they consume themselves [26]. The male, in a display of paternal dedication, typically brings more food than the female. This intensive parental feeding continues for approximately a month before the chicks are gradually weaned off. After fledging, the juveniles must then embark on the challenging learning process of feeding themselves, including mastering the difficult technique of plunge-diving [36]. They will then undertake their first epic journey south to their wintering grounds, often with the guidance and assistance of their parents [37].

Arctic terns are classified as long-lived birds that invest a significant amount of time and energy into raising only a small number of young, a reproductive strategy characteristic of K-selected species [38]. A 1957 study conducted on the Farne Islands estimated an annual survival rate of a respectable 82% [39]. Clearly, they’re built for the long haul.

Gallery

• Nesting with an egg

• A chick, utterly reliant on its parents for a brief time

• An adult with a juvenile, preparing for the inevitable journey

• A juvenile, already looking vaguely unimpressed with the world

Ecology and behaviour

The dietary habits of the Arctic tern are, predictably, somewhat fluid, adapting to both geographical location and seasonal availability, but the underlying principle remains consistent: it is overwhelmingly carnivorous . In the vast majority of cases, its sustenance comes from small fish or various marine crustaceans [12] [24]. Fish species constitute the most critical component of its diet, accounting for a greater proportion of the total biomass consumed than any other food source. The preferred prey fish are typically immature (one to two-year-old) shoaling species such as herring , cod , sandlances , and capelin [13]. Among the diverse marine crustaceans that form part of its diet are amphipods , various crabs , and plentiful krill . On occasion, these opportunistic birds will also consume molluscs , marine worms, or even berries when available, and in their northern breeding grounds, they are not above supplementing their diet with insects [34].

Arctic terns employ a distinct foraging technique, sometimes executing shallow dips to the water’s surface to snatch prey swimming just beneath. When breeding, they may also engage in aerial pursuits, deftly chasing insects on the wing [34]. It is also theorized, rather amusingly given their diminutive stature, that Arctic terns may occasionally engage in kleptoparasitism —the act of stealing food from other animals. This involves swooping aggressively at other birds to startle them into releasing their freshly caught prey [34]. Several species are targeted in these audacious raids, including conspecifics (other Arctic terns ), other tern species (like the common tern ), and even some auk and grebe species [26]. Apparently, no one is safe from a hungry tern with an attitude.

While nesting, Arctic terns find themselves particularly vulnerable to predation by opportunistic cats and a variety of other terrestrial animals [12]. Beyond merely competing for prime nesting real estate, the larger herring gull poses a significant threat, unhesitatingly stealing both eggs and fragile hatchlings. The naturally camouflaged eggs offer some degree of protection, as do the strategic selection of isolated nesting sites [36]. Scientists have even experimented with erecting bamboo canes around tern nests, and while they observed fewer predation attempts in these “caned” areas compared to control zones, the canes did not ultimately reduce the probability of successful predation once an attempt was made [40]. It seems some predators are simply too determined. While out foraging, skuas , gulls, and other tern species will frequently harass Arctic terns , attempting to steal their hard-won food [41]. A bird’s life, it seems, is a constant struggle.

Gallery

• An adult, likely contemplating its next absurdly long flight

• Successfully procured an eel. The small victories.

• Hovering with food over the nest. Parental duties, begrudgingly fulfilled.

• Defending its offspring. Don’t even think about it.

• A juvenile, still figuring out how to be this perpetually busy.

Conservation status

The global population of the Arctic tern is estimated to exceed two million individuals, with a significant portion—more than half—residing in Europe. Its breeding range is, as previously established, remarkably vast. And while the overall population is thought to be in a state of gradual decline, the species is currently assessed as a species of least concern by the IUCN [1]. A testament to its resilience, or perhaps simply the sheer number of them, making a decline less immediately catastrophic.

Arctic terns are among the species afforded protection under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds [42], a small comfort for a bird that effectively ignores human-drawn borders.

Historically, the population in New England suffered significant reductions in the late nineteenth century, a direct consequence of relentless hunting for the insipid millinery trade [26]. Exploitation, unfortunately, persists in western Greenland , where the species’ population has seen a drastic decline since 1950 [43]. In Iceland , the Arctic tern was regionally uplisted to Vulnerable as of 2018, a worrying development primarily attributed to the catastrophic collapse of sandeel (Ammodytes spp.) stocks [44]. It seems even the most resilient travelers are not immune to the consequences of ecosystem collapse.

At the more southerly limits of their extensive range, the Arctic tern has indeed experienced a reduction in numbers. A significant factor contributing to this decline is a critical lack of available food [25]. However, much of these birds’ breeding range is incredibly remote, far from human interference, and across the species as a whole, there is no apparent, widespread negative trend [34]. The Arctic terns’ dispersal patterns are demonstrably affected by changing climatic conditions [45]. Their ability to forage successfully in their Antarctic wintering grounds is intrinsically linked to sea-ice cover, but unlike sedentary breeding species , they possess the remarkable flexibility to relocate to different areas if necessary. This adaptability makes them a valuable control species for scientists investigating the broader impacts of climate change on less mobile breeding populations [46].

Cultural depictions

The Arctic tern , despite its unassuming appearance, has managed to grace the postage stamps of several countries and dependent territories. These territories include Åland , Alderney , and the Faroe Islands , while sovereign nations like Canada , Finland , Iceland , and even Cuba have featured it [47]. A surprisingly diverse fan club for a bird that just wants to be left alone to migrate.

In a moment of questionable comedic genius, the Arctic tern was prominently featured in a sketch on the improv comedy television show Whose Line Is It Anyway? , involving the familiar faces of Colin Mochrie and Ryan Stiles [48]. During this particular sketch, Colin, with his characteristic deadpan delivery, suggested that the call of the Arctic tern bore an uncanny resemblance to the name of the popular boy band, the Backstreet Boys . One can only assume the terns were not amused.