Sterna hirundo

Common terns live up to their Dutch name 'fish thief'. They grab small fish out of the water in less than no time by diving straight downwards and flying back up directly with their loot. They are very common along the coast, but also along lakes and rivers. They nest and hunt in the Netherlands from the end of March till early November. They often breed in colonies, preferably on marshes, beach plains, low dunes or islands. However nowadays its not unusual to find them nesing on or in the vicinity of buildings (such as roofs, industrial areas and parking areas). Common terns spend the winter in Africa.

A medium-sized (13-16 inches) tern, the Common Tern in summer is most easily identified by its solid black cap, deeply-forked tail, black-tipped orange bill, and dark wing tips. In winter, this species becomes duller on the head and face, becoming dark-billed and pale headed while retaining conspicuous black eye-patches connected to a black hood. This species may be distinguished from the similarly-sized Forster’s Tern (Sterna forsteri) by that species’ pale wing tips and (in winter) white hood. Male and female Common Terns are similar to one another in all seasons. The Common Tern occurs across much of the world. In North America, this species breeds in a number of inland and coastal sites in the northeastern U.S.and southern Canada, wintering from the Gulf coast south to southern South America. In the Old World, this species breeds in the mid-latitudes throughout Europe, Asia, and North Africa, wintering in coastal Africa, South Asia, and Australasia. Common Terns primarily breed on rocky or sandy islands and beaches. In winter, this species may be found on beaches or, while feeding, in near-shore waters. Common Terns mainly eat small fish, but may eat small invertebrates, including insects and crustaceans, as they become available. Common Terns may be most easily seen standing or walking along the shore or on the beach, where their dark wing tips and (in summer) black-tipped orange bill may be most apparent. With the aid of binoculars, it may also be possible to observe this species feeding by diving headfirst into the water. Common Terns are most active during the day.

Threat Status: Least concern

Common terns are found from northern Canada south to the Caribbean Sea, as well as throughout Europe, Northern Asia, North Africa, and the Middle East. Some populations of common terns winter in the south to Peru and Argentina.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); neotropical (Native )

Belgian Coast, Belgian Exclusive Economic Zone, Djibouti, Eritrea, European waters (ERMS scope), Gulf of Maine, Gulf of Mexico, Irish Exclusive economic Zone, Kenya, Madagascar, Mozambique, New Zealand Exclusive Economic Zone, North West Atlantic, Northern Hemisphere, Polish Exclusive Economic Zone, Portuguese Exclusive Economic Zone, Red Sea, Somalia, South Africa (country), Spanish Exclusive Economic Zone, Swedish Exclusive Economic Zone, Tanzania, United Kingdom Exclusive Economic Zone, Wimereux

North America; coastal range extends from Labrador to North Carolina

The Common Tern has a circumpolar distribution and can be found breeding in most of Europe, Asia and North America except the extreme north and south. It winters further south, being found along the coast and inland of South America down to the Falkland Islands (Islas Malvinas), along the coast of Africa excluding the north, along parts of the Arabian Peninsula and the whole coast of India, and throughout much of south-east Asia and Australasia (excluding New Zealand)¹.

Common terns are found from northern Canada south to the Caribbean Sea, as well as throughout Europe, Northern Asia, North Africa, and the Middle East. Some populations of common terns winter in the south to Peru and Argentina.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDING: northern Alberta across central Ontario and southern Quebec to southern Labrador, south to eastern Washington, southeastern Alberta, northeastern Montana, North Dakota, northeastern South Dakota, central Minnesota, northeastern Illinois, northwestern Indiana, southern Michigan, northern Ohio, northwestern Pennsylvania, central and northern New York, and northwestern Vermont, locally along coast to North Carolina, and locally on Gulf Coast and Bermuda, Greater Antilles, and Netherlands Antilles (AOU 1983, van Halewyn and Norton 1984). In Old World. Nonbreeders occur in summer at James Bay, throughout Great Lakes region, along Atlantic-Gulf coast, south in Middle America to Costa Rica, and throughout West Indies. NON-BREEDING: Baja California and South Carolina to Peru and northern Argentina (AOU 1983); rare in Hawaii. In Old World.

East coast of North America to interior Canada. South to Caribbean. Europe, coasts of Africa. Asia, including Mongolia and Tibet. South to Japan and Australia.

Because the coloring of common terns changes significantly as seasons change, they are often difficult to identify from plumage alone. They are most easily identified by their black head and red bill. The tail is forked and the tail feathers are more elongated than those of most terns. The wings are pointed and the inner and outer parts of each wing are the same width. The body of common terns is whitish-gray and the underparts are much paler than the upperparts, particularly in adult terns. The female is usually smaller than the male, although only slightly. The bill is usually pointed downward when the tern flies. Other notable characteristics include an exceptionally powerful head and neck and unusually long legs, which distinguish them from other terns such as Arctic terns.

Common terns are 37 cm long, on average, and have a wingspan of 27 cm.

Average length: 37 cm.

Average wingspan: 27 cm.

Sexual Dimorphism: sexes alike; male larger

Average mass: 120 g.

Because the coloring of common terns changes significantly as seasons change, they are often difficult to identify from plumage alone. They are most easily identified by their black head and red bill. The tail is forked and the tail feathers are more elongated than those of most terns. The wings are pointed and the inner and outer parts of each wing are the same width. The body of common terns is whitish-gray and the underparts are much paler than the upperparts, particularly in adult terns. The female is usually smaller than the male, although only slightly. The bill is usually pointed downward when the tern flies. Other notable characteristics include an exceptionally powerful head and neck and unusually long legs, which distinguish them from other terns such as Arctic terns.

Common terns are 37 cm long, on average, and have a wingspan of 27 cm.

Average length: 37 cm.

Average wingspan: 27 cm.

Sexual Dimorphism: sexes alike; male larger

Average mass: 120 g.

Length: 37 cm

Weight: 120 grams

Length: 32-38 cm, Wingspan: 79-81 cm

Length: 31-38 cm. Plumage: tail, rump, back and wings pale grey; collar on hindneck and below white; black cap on head; forehead white in non-breeding bird; tail does not extend beyond wings; outer web of outer primary and tips of primaries diffuse black. Immature like adult but with some brown remaining from juvenile plumage; dusky along trailing edge of secondaries. Bare parts: iris dark brown; bill black (red in breeding plumage) black with reddish base in immature; feet and legs dull red or red-brown (scarlet in breeding birds). Habitat: seashores and estuaries, sometimes inland water bodies. Palearctic migrant. <389><391><393>

Common terns almost always reside in colonies. The colonies tend to be along ocean coasts, although they are also found on the shores of large lakes. The two things necessary for a colony of terns, or a "ternery," are isolation from predators and a reliable source of food nearby. The birds also must be able to communicate visually and vocally with the rest of the colony from their nests. They nest among rocks and cliffs.

Habitat Regions: temperate ; terrestrial ; saltwater or marine ; freshwater

Aquatic Biomes: lakes and ponds; coastal

Habitat and Ecology

Systems

• Terrestrial
• Freshwater
• Marine

Common terns almost always reside in colonies. The colonies tend to be along ocean coasts, although they are also found on the shores of large lakes. The two things necessary for a colony of terns, or a "ternery," are isolation from predators and a reliable source of food nearby. The birds also must be able to communicate visually and vocally with the rest of the colony from their nests. They nest among rocks and cliffs.

Habitat Regions: temperate ; terrestrial ; saltwater or marine ; freshwater

Aquatic Biomes: lakes and ponds; coastal

Depth range based on 1938 specimens in 1 taxon.
Water temperature and chemistry ranges based on 952 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 2.371 - 29.128
  Nitrate (umol/L): 0.102 - 16.868
  Salinity (PPS): 6.428 - 37.431
  Oxygen (ml/l): 4.582 - 8.081
  Phosphate (umol/l): 0.052 - 0.890
  Silicate (umol/l): 0.609 - 11.419

Graphical representation

Temperature range (°C): 2.371 - 29.128

Nitrate (umol/L): 0.102 - 16.868

Salinity (PPS): 6.428 - 37.431

Oxygen (ml/l): 4.582 - 8.081

Phosphate (umol/l): 0.052 - 0.890

Silicate (umol/l): 0.609 - 11.419
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Comments: Seacoasts, estuaries, bays, lakes, rivers, and marshes. Nests on sandy, pebbly, or stony beaches, matted vegetation, marsh islands, and grassy areas; typically on isolated, sparsely vegetated islands in large lakes or along coast, also in rivers. Breeds successfully on human-made islands, including navigational aids or cribs (Karwowski et al. 1995). See Spendelow and Patton (1988) and Ramos and del Nevo (1995) for further details on nesting habitat in different regions.

Coastal and inland waters including lakes, ocean, bays and beaches.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Arrives in breeding areas April-May (Bent 1921). Migration in Costa Rica occurs late September to mid-November and April-May (Stiles and Skutch 1989).

Moves south of North America to warmer waters for winter.

The diet of common terns is usually limited to fishes. Often, if food is particularly abundant, the terns will catch more fish than necessary. Common terns sometimes catch fish that are too big for them to swallow. This, combined with their tendency to catch as much as is available even if it is not needed, explains why it is not unusual to see fish scattered around terns' nesting grounds. At the beginning of the breeding season, terns may eat insects, annelids, and echinoderms in addition to fish. However, throughout the later parts of the breeding season, the tern's diet is much more limited.

These terns are very good at catching insects. Many have been reported to fly near the surface of the water and pick insects off the surface while in flight. It is rare for them to eat dead food. They usually fly at great heights before diving for their prey, a behavior uncommon in other terns. The terns dive into the water after a fish, come to the surface, shake the water from themselves, and fly off with the fish. When a solitary tern catches fish in the same spot repeatedly, other terns from its colony join it.

Foods eaten include: "Food fishes," such as whiting, herring, haddock; sand launces; insects; crabs, shrimp, and other crustaceans; annelids; mollusks; fish eggs; and in certain cases, echinoderms. Terns that nest near bodies of fresh water often consume minnows in place of fish like herring and whiting.

Animal Foods: fish; eggs; insects; mollusks; aquatic or marine worms; aquatic crustaceans; echinoderms

The diet of common terns is usually limited to fishes. Often, if food is particularly abundant, the terns will catch more fish than necessary. Common terns sometimes catch fish that are too big for them to swallow. This, combined with their tendency to catch as much as is available even if it is not needed, explains why it is not unusual to see fish scattered around terns' nesting grounds. At the beginning of the breeding season, terns may eat insects, annelids, and echinoderms in addition to fish. However, throughout the later parts of the breeding season, the tern's diet is much more limited.

These terns are very good at catching insects. Many have been reported to fly near the surface of the water and pick insects off the surface while in flight. It is rare for them to eat dead food. They usually fly at great heights before diving for their prey, a behavior uncommon in other terns. The terns dive into the water after a fish, come to the surface, shake the water from themselves, and fly off with the fish. When a solitary tern catches fish in the same spot repeatedly, other terns from its colony join it.

Foods eaten include: "Food fishes," such as whiting, herring, haddock; sand launces; insects; crabs, shrimp, and other crustaceans; annelids; mollusks; fish eggs; and in certain cases, echinoderms. Terns that nest near bodies of fresh water often consume minnows in place of fish like herring and whiting.

Animal Foods: fish; eggs; insects; mollusks; aquatic or marine worms; aquatic crustaceans; echinoderms

Primary Diet: carnivore (Piscivore )

Comments: Eats mainly small fishes (sometimes also crustaceans and insects) obtained at surface of water by diving from air. Susceptible (especially females just prior to laying) to poisoning from dinoflagellate toxin accumulated in fishes (Nisbet 1983). Pair may defend feeding territory away from nest, especially prior to incubation (Ehrlich et al. 1992).

Fish, mainly. Also eats shrimp and other crustaceans, insects, marine worms, squid, and leeches.

Common terns have an impact on populations of the prey they eat and are an important food source for their predators. Occasionally the fish they catch and do not eat are eaten by other scavenging animals living in the same area.

When a predator comes too close to a tern colony, any terns that spot the predator begin to call loudly to the rest of the colony. Adult terns come over to mob the predator while the chicks take cover in the high grass or in their nests.

Also, the sheer number of terns in a colony aids in the strategy of "passive avoidance". In other words, the probability of any one tern being harmed by a predator is much less because of the number of other terns that the predator could choose instead.

A common tactic among members of colonies, and in fact among all members of tern colonies and gull colonies, is called a "panic." This means that an entire colony of terns flies up making noise, falls silent suddenly, and then swoops back down toward the ground. This can be very threatening to potential predators and often assures that the colony will be left alone, particularly by smaller predators such as blue jays or grackles.

Known predators include: red foxes (Vulpes vulpes), raccoons (Procyon lotor), striped skunks (Mephitis mephitis), minks (genus Mustela), long-tailed weasels (Mustela frenata), squirrels (subfamily Sciurinae), dogs (Canis lupus familiaris), cats (Felis silvestris), rats (Rattus norvegicus), gulls (genus Larus), herons (family Ardeidae), hawks (family Accipitridae), falcons (family Falconidae), owls (family Strigidae), blue jays (Cyanocitta cristata), grackles (genus Quiscalus), reptiles (class Reptilia) and ants (family Formicidae).

Known Predators:

• red foxes (Vulpes_vulpes)
• raccoons (Procyon_lotor)
• striped skunks (Mephitis_mephitis)
• minks (Mustela)
• long-tailed weasels (Mustela_frenata)
• squirrels (Sciurinae)
• domestic dogs (Canis_lupus_familiaris)
• domestic cats (Felis_silvestris)
• brown rats (Rattus_norvegicus)
• gulls (Larus)
• herons (Ardeidae)
• hawks (Accipitridae)
• falcons (Falconidae)
• owls (Strigidae)
• blue jays (Cyanocitta_cristata)
• grackles (Quiscalus)
• reptiles (Reptilia)
• ants (Formicidae)

Common terns have an impact on populations of the prey they eat and are an important food source for their predators. Occasionally the fish they catch and do not eat are eaten by other scavenging animals living in the same area.

When a predator comes too close to a tern colony, any terns that spot the predator begin to call loudly to the rest of the colony. Adult terns come over to mob the predator while the chicks take cover in the high grass or in their nests.

Also, the sheer number of terns in a colony aids in the strategy of "passive avoidance". In other words, the probability of any one tern being harmed by a predator is much less because of the number of other terns that the predator could choose instead.

A common tactic among members of colonies, and in fact among all members of tern colonies and gull colonies, is called a "panic." This means that an entire colony of terns flies up making noise, falls silent suddenly, and then swoops back down toward the ground. This can be very threatening to potential predators and often assures that the colony will be left alone, particularly by smaller predators such as blue jays or grackles.

Known predators include: red foxes (Vulpes vulpes), raccoons (Procyon lotor), striped skunks (Mephitis mephitis), minks (genus Mustela), long-tailed weasels (Mustela frenata), squirrels (subfamily Sciurinae), dogs (Canis lupus familiaris), cats (Felis silvestris), rats (Rattus norvegicus), gulls (genus Larus), herons (family Ardeidae), hawks (family Accipitridae), falcons (family Falconidae), owls (family Strigidae), blue jays (Cyanocitta cristata), grackles (genus Quiscalus), reptiles (class Reptilia) and ants (family Formicidae).

Known Predators:

• red foxes (Vulpes vulpes)
• raccoons (Procyon lotor)
• striped skunks (Mephitis mephitis)
• minks (Mustela)
• long-tailed weasels (Mustela frenata)
• squirrels (Sciurinae)
• domestic dogs (Canis lupus familiaris)
• domestic cats (Felis silvestris)
• brown rats (Rattus norvegicus)
• gulls (Larus)
• herons (Ardeidae)
• hawks (Accipitridae)
• falcons (Falconidae)
• owls (Strigidae)
• blue jays (Cyanocitta cristata)
• grackles (Quiscalus)
• reptiles (Reptilia)
• ants (Formicidae)

Sterna hirundo (Sterna hirundo common tern) preys on:
Sprattus sprattus
Clupea harengus
Ammodytes tobianus
Crangon crangon

Based on studies in:
Scotland (Estuarine)

This list may not be complete but is based on published studies.

10,000 - 1,000,000 individuals

Comments: Breeding population estimates for the early 1980s: 15,200 in Massachusetts, 5800 in Connecticut, 56,000 on Long Island, 4500 in North Carolina, a few dozen on Gulf Coast. Breeding population estimates for the late 1970s: Great Lakes, about 5000 in the U.S., 16,000 in Canada; New Jersey, 9600.

In Massachusetts, loss of eggs and chicks was attributed to nocturnal desertion of nests by adults in response to predation by great horned owl (Nisbet and Welton 1984). Presence of mink can reduce reproductive success (Condor 95:708-711). Nonbreeding: singly or in small loose groups, sometimes in large flocks in migration (Stiles and Skutch 1989).

Common terns communicate mostly with their unusual, hoarse voices, and they have three different, distinct calls. During mating, communication is mainly visual and tactile.

Communication Channels: visual ; tactile ; acoustic

Common terns communicate mostly with their unusual, hoarse voices, and they have three different, distinct calls. During mating, communication is mainly visual and tactile.

Communication Channels: visual ; tactile ; acoustic

Not enough information available.

Not enough information available.

The average lifespan is about 9 to 10 years. The oldest common tern ever recorded was 25 years old.

Range lifespan
Status: wild: 0 (high) years.

Typical lifespan
Status: wild: 9 to 10 years.

Average lifespan
Status: wild: 9-10 years.

The average lifespan is about 9 to 10 years. The oldest common tern ever recorded was 25 years old.

Range lifespan
Status: wild: 0 (high) years.

Typical lifespan
Status: wild: 9 to 10 years.

Average lifespan
Status: wild: 9-10 years.

Maximum longevity: 33 years (wild) Observations: Average lifespan in the wild has been estimated to be 9-10 years (John Terres 1980). Maximum longevity from banding studies is 33 years (http://www.euring.org/data_and_codes/longevity.htm).

During courtship, which begins in April, male terns establish their territories at the colony before beginning what is called "courtship feeding," in which males bring fish to the females as a way of courting them. Premating displays are accompanied by the male tern posturing followed by the two terns circling each other. The males mount the females for one- to two-minute intervals before copulation actually takes place. Common terns are known for wildly flapping their wings during and directly after copulating. Common terns are monogamous.

Mating System: monogamous

Common terns, after migrating to their breeding grounds shortly after the beginning of spring, proceed to find a mate (terns tend to be monogamous); they reproduce in early to mid-summer. It is rare for a pair to produce more than one clutch per summer. They nest among rocks and cliffs. The nests are made up of shells and debris or of dead vegetation. Clutch size is 3, on average, and the chicks hatch in 3 to 4 weeks. Young fledge in 27 to 30 days. Common tern chicks are able to fly by the time they are a month old but do not reach sexual maturity for 3 years.

Breeding interval: It is rare for a pair to produce more than one clutch per summer.

Breeding season: They reproduce from early to mid-summer.

Average eggs per season: 3.

Range time to hatching: 3 to 4 weeks.

Range fledging age: 27 to 30 days.

Average age at sexual or reproductive maturity (female): 3 years.

Average age at sexual or reproductive maturity (male): 3 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average eggs per season: 3.

One of the parents attends the nest at all times after the eggs hatch; the female is often, but not always, the one standing guard. Common terns become very aggressive after their chicks learn to move on their own because of the likelihood that the chicks will be harmed or killed by predators. Both males and females bring food back to the nest, but males are usually more involved in feeding than females are. Chicks are semiprecocial. Young terns usually learn to fly when they are 27 to 30 days old.

Parental Investment: no parental involvement; pre-hatching/birth (Protecting); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female)

During courtship, which begins in April, male terns establish their territories at the colony before beginning what is called "courtship feeding," in which males bring fish to the females as a way of courting them. Premating displays are accompanied by the male tern posturing followed by the two terns circling each other. The males mount the females for one- to two-minute intervals before copulation actually takes place. Common terns are known for wildly flapping their wings during and directly after copulating. Common terns are monogamous.

Mating System: monogamous

Common terns, after migrating to their breeding grounds shortly after the beginning of spring, proceed to find a mate (terns tend to be monogamous); they reproduce in early to mid-summer. It is rare for a pair to produce more than one clutch per summer. They nest among rocks and cliffs. The nests are made up of shells and debris or of dead vegetation. Clutch size is 3, on average, and the chicks hatch in 3 to 4 weeks. Young fledge in 27 to 30 days. Common tern chicks are able to fly by the time they are a month old but do not reach sexual maturity for 3 years.

Breeding interval: It is rare for a pair to produce more than one clutch per summer.

Breeding season: They reproduce from early to mid-summer.

Average eggs per season: 3.

Range time to hatching: 3 to 4 weeks.

Range fledging age: 27 to 30 days.

Average age at sexual or reproductive maturity (female): 3 years.

Average age at sexual or reproductive maturity (male): 3 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average eggs per season: 3.

One of the parents attends the nest at all times after the eggs hatch; the female is often, but not always, the one standing guard. Common terns become very aggressive after their chicks learn to move on their own because of the likelihood that the chicks will be harmed or killed by predators. Both males and females bring food back to the nest, but males are usually more involved in feeding than females are. Chicks are semiprecocial. Young terns usually learn to fly when they are 27 to 30 days old.

Parental Investment: no parental involvement; pre-hatching/birth (Protecting); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female)

Eggs are laid mostly May-July. Clutch size is 2-3. Incubation lasts 21-27 days, mainly by female. Both sexes tend young, which may leave nest after 3 days (return for brooding) and first fly at about 4 weeks. May lay 2 clutches/year, but second brood rarely fledges. In New York, breeding season was timed to overlap with seasonal increase in food abundance, but food availability began to decline before period of peak demand for food by chicks (Safina and Burger 1988); in a two-year study, fish abundance affected reproductive performance (Safina et al. 1988).

First breeds at 3-4 years old. Nest built by both partners on bare ground, usually in a colony. 1-3 eggs, incubated by both sexes for 21-25 days. Young are fed by both parents. First capable of flight around 22-28 days old.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 10
Specimens with Barcodes: 20
Species With Barcodes: 1

The Michigan DNR considers common terns to be threatened in Michigan. Human interference has caused health and habitat problems for the terns. Human disturbance in the form of deliberately damaging eggs, chicks, and nests has become a problem because the coastal areas where terns nest are also areas where people picnic and sunbathe. Nature photographers and bird watchers, while meaning no harm, sometimes disturb the terns when they are nesting. Humans also cause problems for the terns through environmental pollution with chemicals, which weaken the eggshells and cause birth defects. Some adults and chicks die when they become tangled in netting or plastic. In the nineteenth century, terns were removed from nearly all of their former habitats when they were exploited commercially for their eggs and their feathers.

IUCN Red List of Threatened Species: least concern

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: threatened

Regular passage visitor and migrant breeder?

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
• 2004
  Least Concern

The Michigan DNR considers common terns to be threatened in Michigan. Human interference has caused health and habitat problems for the terns. Human disturbance in the form of deliberately damaging eggs, chicks, and nests has become a problem because the coastal areas where terns nest are also areas where people picnic and sunbathe. Nature photographers and bird watchers, while meaning no harm, sometimes disturb the terns when they are nesting. Humans also cause problems for the terns through environmental pollution with chemicals, which weaken the eggshells and cause birth defects. Some adults and chicks die when they become tangled in netting or plastic. In the nineteenth century, terns were removed from nearly all of their former habitats when they were exploited commercially for their eggs and their feathers.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: threatened

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5B - Secure

United States

Rounded National Status Rank: N5B - Secure

Rounded Global Status Rank: G5 - Secure

Evidence exists of declining numbers in coastal and interior populations. There is no official conservation status.

Major Threats

Comments: Populations initially were decimated by the millinery trade. Major current threats in different areas include nest-site competition from expanding ring-billed gull populations (Great Lakes region); predation by owls, black-crowned night heron, rats, or herring gull; loss of beach habitat; flooding and rising water levels (Great Lakes region); human disturbance; and possibly biocide contamination (Buckley and Buckley 1984).

Conservation Actions

Management Requirements: Gull control has benefited this species in Maine (Buckley and Buckley 1984). See Minsky (1981) for discussion of tern management on Cape Cod.

There are no known adverse affects of common terns on humans.

In the nineteenth century, terns were exploited commercially for their eggs and feathers.

Positive Impacts: body parts are source of valuable material

There are no known adverse affects of common terns on humans.

In the nineteenth century, terns were exploited commercially for their eggs and feathers.

Positive Impacts: body parts are source of valuable material