Common Tern Profile: Facts, Habitat, Call, Migration, Diet

common tern-

The common tern, scientifically known as Sterna hirundo, is a fascinating seabird that belongs to the Laridae family. These birds are known for their graceful flight and distinctive appearance, with long wings and forked tails.

Common Tern Profile: Facts, Habitat, Call, Migration, Diet

While common tern populations are generally stable, they face threats from habitat loss, pollution, and disturbances to their breeding sites. Conservation efforts are underway to protect their nesting areas and ensure the long-term survival of this beautiful seabird species.

Global Distribution: Common Terns Around the World

The common tern, a remarkable seabird known scientifically as Sterna hirundo, has a truly global presence. This means that these birds can be found all around the world, particularly in regions with temperate and subarctic climates. With their remarkable adaptability, common terns have established breeding populations across Europe, Asia, and North America. This widespread distribution reflects their ability to thrive in diverse habitats and environments.

Migration Patterns: Seasonal Movements of the Common Tern

The common tern is renowned for its strong migratory instincts, embarking on extensive journeys to winter in coastal tropical and subtropical regions. During the breeding season, these birds exhibit distinct plumage characteristics, featuring mild grey upperparts and white to very mild grey underparts. Additionally, breeding adults sport a striking black cap atop their heads, complemented by orange-red legs and a slender, pointed bill.

Plumage Variation: Bill Color and Subspecies Differences

The bill color of the common tern varies depending on the subspecies, with some featuring predominantly pink bills with black tips, while others have entirely black bills. These subtle differences in bill coloration contribute to the unique appearance of each subspecies and aid in their identification.


Species Differentiation: Similar Tern Varieties

While the common tern shares similarities with other tern species, such as the Arctic tern, they can be distinguished based on plumage details, leg and bill coloration, and vocalizations. Despite coexisting in some areas, each species has distinctive features that set them apart from one another.

Versatile Breeding Habits: Adaptable Nesting Preferences

The common tern displays remarkable versatility in its choice of breeding habitats, nesting in a wider range of environments than any other member of the tern family. They are known to nest on various flat, poorly vegetated surfaces near water, including beaches, islands, and even artificial substrates like floating rafts. This adaptability allows them to thrive in diverse ecosystems and successfully raise their young in different environments.

Physical Characteristics: Identifying Common Terns

Common terns possess distinct physical features that make them easy to identify. They have sleek, slender bodies with pointed wings and deeply forked tails, giving them a graceful appearance in flight. One of their most prominent features is the black cap on their heads, which contrasts sharply with their white bodies. Their sharp, pointed bills are perfectly adapted for capturing fish and other aquatic prey, while their long, slender legs enable them to wade through shallow waters with ease.

The nominate subspecies of the common tern measures between 31 to 35 cm (12 to 14 inches) in length, inclusive of a 6 to 9 cm (2.4 to 3.5 inches) fork in the tail, with an impressive wingspan spanning between 77 to 98 cm (30 to 39 inches). It typically weighs between 110 to 141 g (3.9 to 5.0 oz), making it a relatively lightweight bird compared to other species.

Distinctive Features of Breeding Adults

Breeding adults of the common tern exhibit distinct physical features, including pale grey upperparts and very pale grey underparts. They are characterized by a black cap atop their heads, complemented by striking orange-red legs and a slender, pointed bill. The bill may vary in coloration, appearing either predominantly pink with a black tip or entirely black, depending on the specific subspecies.

Seasonal Changes in Plumage

As the summer progresses, notable changes occur in the common tern’s plumage. The upper wings, initially pale grey, undergo transformation as the dark feather shafts of the outer flight feathers become exposed. This process results in the emergence of a grey wedge on the wings, adding to the bird’s distinctive appearance during breeding season.

Additional Plumage Details

The rump and tail feathers of the common tern are predominantly white, contributing to its overall coloration. Notably, the long tail of the bird does not extend beyond the folded wingtips when the bird is at rest, a distinguishing feature that sets it apart from related species such as the Arctic and roseate terns. Furthermore, there are no significant differences in appearance between male and female common terns, with both sexes exhibiting similar plumage characteristics.

Vulnerabilities to Predation

Eggs and young common terns are susceptible to predation by a variety of mammals, including rats and American mink, as well as larger birds such as gulls, owls, and herons. These predators pose significant threats to the survival of tern nests and offspring, requiring protective measures to safeguard breeding colonies.

Parasitic Infections and Health Concerns

While common terns may face infestations of lice, parasitic worms, and mites, instances of blood parasites appear to be rare. However, these infections can still impact the overall health and well-being of the birds, necessitating measures to mitigate their spread and effects.

Conservation Status and Population Trends

The common tern maintains a large population and extensive breeding range, contributing to its classification as a species of least concern in terms of conservation status. However, populations in North America have experienced significant declines in recent decades, highlighting ongoing challenges and threats faced by the species.

Environmental Threats and Conservation Efforts

Despite international regulations aimed at protecting common tern populations, certain regions still face threats from habitat loss, pollution, and disturbances to breeding colonies. Efforts to address these environmental challenges include habitat restoration initiatives, pollution control measures, and the establishment of protected areas to safeguard breeding grounds and nesting sites.

Behavior and Diet: Skilled Hunters of the Skies

These seabirds are masters of the hunt, specializing in capturing small fish, crustaceans, and insects. Using their keen eyesight and agile flight capabilities, common terns employ a unique diving technique to catch their prey. With remarkable precision, they plunge headfirst into the water from above, swiftly seizing unsuspecting fish beneath the surface. Additionally, common terns are adept at aerial acrobatics, effortlessly maneuvering through the air as they swoop and dive to catch flying insects or small fish. This combination of hunting techniques allows them to efficiently obtain the nutrients they need to thrive in their coastal habitats.

Breeding Habits: Nests and Colonies

During the breeding season, which typically occurs during the warmer months of the year, common terns exhibit fascinating nesting behavior. They gather in large colonies, forming bustling communities near coastal areas, islands, or inland lakes. Here, they meticulously construct their nests on the ground using a variety of materials such as grass, twigs, and shells. These nests are strategically placed in open areas, providing easy access to food sources like fish and insects. This communal nesting behavior allows them to benefit from safety in numbers and efficient resource utilization.

Nesting Behavior: Construction and Characteristics

The common tern exhibits diverse nesting behaviors, with nests ranging from simple scrapes in sand or gravel to more elaborate structures lined or edged with available debris. These nesting sites are strategically chosen to provide adequate protection and camouflage for the eggs and young chicks.

Reproductive Cycle: Egg Laying and Incubation

Female common terns typically lay up to three eggs per clutch, each bearing dull colors and blotchy patterns that aid in blending into the surrounding environment, particularly on open beaches. Both male and female terns take turns incubating the eggs, a process that lasts approximately 21 to 22 days under normal conditions. However, incubation may be prolonged if the colony is disturbed by potential predators.

Growth and Development: Fledging and Feeding Habits

After hatching, the downy chicks of the common tern undergo a rapid growth process, typically fledging within 22 to 28 days. During this critical period, parental care and protection are essential for the survival of the young birds. Similar to other tern species, common terns primarily feed by plunge-diving into the water to catch fish. While fish comprise a significant portion of their diet, they may also consume mollusks, crustaceans, and various invertebrates, particularly in certain geographical areas.

Plumage Changes in Non-Breeding Adults

During the non-breeding season, adult common terns undergo noticeable changes in plumage. The brown cap characteristic of breeding adults fades, transitioning to white, while the underparts also become predominantly white in coloration. The bill may appear entirely black or feature a black coloration with a pink base, and the legs exhibit a darker pink or black hue.

Distinctive Features of the Upper Wings

In non-breeding adults, the upper wings display a distinct dark area along the front edge known as the carpal bar. This feature serves as a distinguishing characteristic of the common tern’s plumage during this phase.

Timing of Plumage Changes

The timing of plumage changes varies among common terns, with individuals that have not successfully bred often initiating the transition into non-breeding adult plumage from June onwards. However, late July is a more typical timeframe for this molt, with the process suspended during migration. Geographical factors also play a role, with Californian birds typically exhibiting non-breeding plumage during migration.

Juvenile Plumage Characteristics

Juvenile common terns exhibit distinctive plumage characteristics that differentiate them from adults. Their upper wings feature a pale grey coloration with a prominent dark carpal bar. The crown and nape of juveniles are brown, gradually transitioning to a ginger hue on the forehead, which lightens to white by autumn as the bird matures. These plumage features help identify juvenile common terns during their early stages of development.

Plumage Characteristics of Juveniles

Juvenile common terns exhibit distinct plumage characteristics, including upper parts that are ginger with brown and white scaling. Unlike adults, juveniles lack the long outer feathers in their tails, which are a characteristic feature of mature birds.

Post-Juvenile Plumage

Birds in their first post-juvenile plumage, typically remaining in their wintering areas, resemble non-breeding adults but with some distinguishing features. They may have a duskier crown, a dark carpal bar on the upper wings, and often display worn plumage due to their recent transition from juvenile to adult-like plumage.

Development by the Second Year

By their second year, most young common terns have completed the transition to adult-like plumage. At this stage, they are either indistinguishable from adults or exhibit only minor differences, such as a darker bill or a white forehead.

Flight Characteristics

The common tern is known for its agility in flight, capable of executing rapid turns and swoops, hovering in place, and performing vertical take-offs. These aerial maneuvers are essential for hunting prey, evading predators, and navigating across its wide-ranging habitat.

Flight Behavior

When common terns are searching for fish, they typically fly close to the surface of the water when facing a strong headwind, but they soar higher, between 10 to 30 meters (33 to 98 feet) above the water, when flying with a following wind. During migration, they usually maintain an altitude of less than 100 meters (330 feet) and travel at an average speed of 30 km/h (19 mph) in calm conditions.

Migration Patterns

During nocturnal migration flights, common terns fly at a higher speed, averaging between 43 to 54 km/h (27 to 34 mph), and at altitudes ranging from 1,000 to 3,000 meters (3,300 to 9,800 feet). This migration behavior allows them to cover long distances efficiently while conserving energy.

Plumage Moulting

Juvenile common terns begin the transition into adult plumage starting in their first October. The moulting process typically starts with the head, tail, and body plumage, which are replaced first, mostly by February. Subsequently, the wing feathers undergo moulting, completing the transition to adult-like plumage. This moulting process is essential for maintaining optimal flight performance and appearance.

Primary Feather Moult

The moulting process of the primary feathers in common terns occurs in distinct phases. Initially, the innermost feathers are shed, followed by a suspension of replacement during the southern winter, especially for birds remaining in their wintering areas. This moulting sequence recommences in the autumn months.

Secondary Feather Moult

In the second year of life, typically from May to June, a similar moult sequence begins for the secondary feathers. For birds migrating northward, there is a pause in the moult during this period, whereas for those remaining in winter quarters, the moult continues uninterrupted.

Transition to Adult Breeding Plumage

Between February and June of the following year, common terns undergo a significant moult to acquire adult breeding plumage. During this process, approximately 40–90% of feathers are replaced. As the old feathers wear away, the blackish barbs beneath become exposed, gradually transitioning the bird to its distinctive adult appearance.

Wing Feather Ageing

The moult pattern results in the oldest feathers being located closest to the center of the wing. Consequently, as the northern summer progresses, a dark wedge-shaped pattern appears on the wing due to the ageing process of the feathers. This pattern is a characteristic feature observed in common terns during their transition to adult plumage.

Vocal Repertoire

The common tern exhibits a diverse range of vocalizations, which are characterized by a lower pitch compared to similar calls made by Arctic terns. Among its various vocalizations, the most distinctive sound is the alarm call, which is pronounced as “KEE-yah” with stress on the first syllable, unlike the Arctic tern’s stress on the second syllable.

Alarm Calls

The alarm call serves a dual purpose: it acts as a warning to intruders and also functions as a signal for the colony members to quieten down while they assess the potential threat. Additionally, during moments of heightened danger, common terns emit a distinct “kyar” call as they take flight.

Parental Communication

Adult common terns emit a specific “down-slurred keeur” call when approaching the nest while carrying a fish. This call is believed to serve as a means of individual recognition, as chicks emerge from hiding upon hearing their parents produce this sound.

Social Contact Calls

Another common vocalization among common terns is the “kip” call, which is exchanged during social interactions. During aggressive encounters with intruders, common terns emit a rapid “kakakakaka” call, while fighting males produce a staccato “kek-kek-kek” call.

Vocal Recognition

Parents and chicks use vocalizations to locate each other, and siblings can recognize one another’s calls by the twelfth day from hatching. This ability helps maintain the cohesion of the brood and facilitates family communication within the colony.

Migration Patterns

The common tern exhibits strong migratory behavior, with most populations wintering in regions south of their breeding ranges in the temperate and subarctic Northern Hemisphere. During the winter months, these birds can be found in coastal tropical and subtropical areas.

Breeding Range in North America

In North America, the common tern breeds along the Atlantic coast from Labrador to North Carolina. Additionally, breeding populations can be found inland throughout much of Canada, particularly east of the Rocky Mountains. Some colonies also exist in states bordering the Great Lakes and regionally along the Gulf coast.

Caribbean Colonies

Small, partially migratory colonies of common terns are found in the Caribbean, specifically in The Bahamas, Cuba, and off the coast of Venezuela in the Los Roques and Las Aves archipelagos.

European Breeding Range

Across Europe, the common tern breeds extensively, with the highest numbers observed in the northern and eastern parts of the continent. There are also small breeding populations along the North African coast, as well as in the Azores, Canary Islands, and Madeira.

Wintering Areas

During the winter months, most common terns from Europe migrate to regions off western or southern Africa. Birds from southern and western Europe tend to remain north of the equator, while others move further south.

Breeding Range in Asia

The breeding range of the common tern extends across the temperate and taiga zones of Asia, with scattered colonies found along the Persian Gulf and the coast of Iran.

Common tern

Feeding Behavior

Similar to other Sterna terns, the common tern employs plunge-diving as its primary method of feeding, diving from heights of 1–6 meters (3.3–19.7 feet) into both seawater and freshwater bodies such as lakes and rivers. During the dive, the bird may submerge briefly, typically not exceeding 50 cm (20 inches) below the surface. Before diving, the tern adopts a head-down posture with its bill held vertically, scanning for fish. Unlike the Arctic tern’s “stepped-hover” approach or the roseate tern’s high-speed dive, the common tern’s plunge is more direct.

Visual Adaptations

Common terns possess pink oil droplets within the cone cells of their retinas, enhancing contrast and sharpening distance vision, particularly in hazy conditions. This adaptation aids in locating prey while flying or hovering above the water surface.

Prey Preferences

The common tern primarily targets fish ranging from 5–15 cm (2.0–5.9 inches) in length, although the specific species caught depends on availability. When provisioning multiple chicks, terns tend to capture larger prey compared to those with smaller broods. While fish may constitute up to 95% of the diet in some regions, invertebrates also play a significant role, including worms, mollusks, crustaceans, and insects.

Foraging Techniques

In freshwater habitats, common terns may capture large insects like beetles, moths, and cockchafers, either in flight or by picking them off the ground or water surface. Prey is typically caught in the bill and either swallowed whole or carried back to the nest, where adults identify their young by their vocalizations rather than visual cues. Fish bones and hard exoskeletons are regurgitated as pellets, and both adults and chicks defecate away from the nest site, with adults sometimes using this as a defensive tactic against intruders.

Colony Size

Common tern colonies typically consist of fewer than 2,000 pairs, although larger colonies exceeding 20,000 pairs may occasionally occur. Inland colonies tend to be smaller compared to those found along the coast.

Nesting Habits

Common terns often nest alongside other coastal bird species, including Arctic terns, roseate terns, Sandwich terns, black-headed gulls, and black skimmers. During the early stages of the breeding season, these birds may engage in a phenomenon known as a “dread,” where they fly low and swiftly out to sea in silence for reasons that remain unclear.

Nesting Territory

Upon their return to breeding sites, terns may linger for a few days before settling into a territory. The initiation of nesting activity may be influenced by the availability of fish in the area. Terns typically defend only a small nesting area, with distances between nests often as close as 50 cm (20 in), although distances of 150–350 cm (59–138 in) are more common.

Nest Site Reuse

Similar to many bird species, common terns often reuse the same nesting site year after year. There are records of pairs returning to the same site for up to 17 consecutive breeding seasons. Around 90% of experienced birds reuse their former territory, leaving young birds to nest on the periphery, seek out a bereaved mate, or relocate to another colony.

Territory Selection and Defense

Upon arrival in the spring, a male common tern selects a nesting territory within a few days. He is typically joined by his previous mate, unless she is more than five days late, in which case the pair may separate. Territory defense is primarily the responsibility of the male, who repels intruders of both sexes by giving an alarm call, spreading his wings, raising his tail, and bowing his head to display the black cap.

Aggression and Defense

If an intruder persists, the male will engage in a physical altercation, known as bill grappling, until the intruder submits by raising its head to expose the throat. Aerial trespassers are also attacked, often following a joint upward-spiraling flight. Interestingly, wandering chicks are typically tolerated within the colony, a behavior that differs from gull colonies where they may be attacked and killed.

Collective Defense

The nest is defended until the chicks have fledged, and all adults in the colony work together to repel potential predators. This collective defense strategy helps ensure the safety of the nesting site and its inhabitants until the young are capable of fending for themselves.

Courtship Behavior

Pairs of common terns establish or confirm their bond through aerial courtship displays. During these displays, a male and female fly in broad circles, calling continuously, before descending together in zigzag glides. The male may attract the attention of other males if he is carrying a fish. Once on the ground, the male engages in courtship behavior by circling the female with his tail and neck raised, head pointing down, and wings partially open. If the female responds positively, they may adopt a posture with their heads pointed skywards.

Nesting Site Selection

After courtship is complete, the male creates a shallow depression in the sand while the female scratches in the same spot. Several trials may occur until the pair selects a site for the actual nest. Eggs may be laid directly on the bare sand, gravel, or soil, but a lining of debris or vegetation is often added if available. The saucer-shaped scrape is typically around 4 cm deep and 10 cm across, although it may extend up to 24 cm wide including surrounding decorative materials. How AI, ChatGPT maximizes earnings of many people in minutes

Breeding Success and Nesting Material

Breeding success in areas prone to flooding has been improved by providing artificial mats made from eelgrass, which encourage terns to nest in higher, less vulnerable areas. The common tern tends to use more nest material than other tern species, with roseate terns often nesting in areas with more vegetation. Terns demonstrate remarkable skill in locating their nests within a large colony, facilitated by adaptations to their wind-blown and tidal environment.

Egg Production and Incubation

The peak time for egg production is early May, with some birds laying later in the month or in June. Clutches typically consist of three eggs, although larger clutches may result from multiple females laying in the same nest. Eggs are cream, buff, or pale brown, marked with streaks, spots, or blotches of black, brown, or grey for camouflage. Incubation lasts 21–22 days, primarily by the female, but occasionally by both sexes. Motivation – Mind – Success – Thinking – Productivity – Happiness

Chick Development and Fledging

Upon hatching, the precocial downy chicks are yellowish with black or brown markings, resembling the eggs. They fledge in 22–28 days, typically around 25–26 days. Fledged juveniles are fed on the nest for about five days before accompanying adults on fishing expeditions. Young birds may receive supplementary feeds from parents until the end of the breeding season and beyond, with records of adults feeding offspring during migration and in wintering grounds.

Nest Defense and Behavior

Like many tern species, the common tern exhibits strong defensive behavior to protect its nest and young. It may harass humans, dogs, muskrats, and other diurnal birds, although it rarely makes physical contact with intruders, typically veering off at the last moment. Adults can distinguish between individuals, showing more intense attacks towards familiar individuals compared to strangers. Nocturnal predators like rats can pose a significant threat, leading to colony abandonment for up to eight hours in the presence of great horned owls. Business – Money Making – Marketing – E-commerce

Breeding Frequency and Success

Common terns typically breed once a year, with the possibility of second clutches if the first is lost. Rarely, a second clutch may be laid and incubated while some chicks from the first clutch are still being fed. The first breeding attempt usually occurs at four years of age, although it may happen as early as three years. The average number of young per pair surviving to fledge varies depending on factors such as colony conditions, ranging from zero in flood events to over 2.5 in favorable years.

Lifespan and Longevity

In the wild, common terns have been documented to live up to 23 years in North America and 33 years in Europe, although a typical lifespan is around 12 years. Longevity can vary due to factors such as predation, environmental conditions, and availability of food sources. Despite potential threats and challenges, individuals of this species can achieve considerable lifespans, contributing to the overall population dynamics and genetic diversity of the species. Health books, guides, exercises, habits, Diets, and more

Predation Threats

Predation poses a significant threat to common tern populations, with various predators targeting both eggs and chicks. While rats are known to raid tern nests and may even store large quantities of eggs in caches, the American mink emerges as a key predator of hatched chicks, particularly in regions where it has been introduced, such as North America and Scotland.

Avian Predators

Due to their nesting habits on islands, common terns are more commonly preyed upon by other birds rather than mammals. The ruddy turnstone is known to pilfer eggs from unattended nests, while gulls may prey on chicks. Additionally, great horned owls and short-eared owls pose a threat to both adult terns and their chicks. Black-crowned night herons may also target small chicks as prey. Fitness – Meditation – Diet – Weight Loss – Healthy Living – Yoga

Aerial Predators

In addition to ground-based predators, common terns face threats from aerial predators such as merlins and peregrine falcons. These birds of prey may target flying terns, taking advantage of their speed and agility. Flocking behavior among terns likely serves as a defense mechanism against fast-flying predators, helping to confuse and evade attacks.

Conservation Status

The common tern holds the status of “least concern” on the IUCN Red List, indicating a relatively stable population and widespread distribution. Estimates suggest a vast population of 1,600,000–4,600,000 mature individuals, with breeding territories spanning approximately 29,200,000 square kilometers. RPM 3.0 – 60% CONVERSION & Money for Affiliate Marketing

Breeding Distribution

Breeding populations are estimated at 250,000–500,000 pairs, with the majority breeding in Asia and approximately 140,000 pairs in Europe. North America hosts fewer than 80,000 pairs, primarily along the northeast Atlantic coast, with a declining population of fewer than 10,000 pairs in the Great Lakes region.


Common terns face various threats, including habitat loss due to construction, pollution, vegetation growth, and disturbance by human activities such as recreation, transportation, and dog walking. Natural flooding events can also result in nest losses, and colonies are vulnerable to predation by rats and large gulls. Competition for nest sites with gulls further exacerbates the situation, and some populations are hunted in the Caribbean for commercial sale as food. Bird accessories on Amazon

Conservation Measures

To enhance breeding success and mitigate threats, conservation efforts include the deployment of floating nest rafts, artificial islands, and other man-made nest sites. Human disturbance is minimized through proactive measures such as controlled burns to clear overgrown vegetation and deliberate disturbance to deter gulls. Additionally, legislation such as the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) and the US-Canada Migratory Bird Treaty Act of 1918 provides a framework for conservation strategies and mandates the protection of common terns and their habitats. These agreements emphasize species and habitat conservation, research, education, and implementation of conservation measures.

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