Caspian tern

Hydroprogne caspia

Photo by Vladimirs Suščinskis (Ornitofaunistika)

Common name:
Caspian tern (en); gaivina-grande (pt); sterne caspienne (fr); pagaza piquirroja (es); raubseeschwalbe (de)

Taxonomy:
Order Charadriiformes
Family Sternidae

Range:
This species has a cosmopolitan but scattered distribution, breeding in the Baltic sea, in eastern Europe and central Asia from the southern Ukraine to western Mongolia, along the coast of China, in West Africa, around the eastern Mediterranean, in Pakistan, in Sri Lanka, in Madagascar and the coasts of southern Africa, in Australia and New Zealand, in the great lakes of North America, in the western United States and along the coast of Texas. Outside the breeding season they also spread along most of the coasts and inland wetlands of Central America, Africa and India.

Size:
The largest tern in the world, the Caspian tern is 48-56 cm long and has a wingspan of 127-140 cm. They weigh 580-780 g.

Habitat:
These birds are found in various coastal and inland wetlands, including coastal waters and estuaries, bays, harbours, coastal lagoons, saltmarshes, lakes, inland seas, large rivers, creeks, reservoirs and sewage ponds. They breed in sandy beaches, sand dunes, rocky coasts, sheltered reefs and islands with sparse vegetation and flat or gently sloping margins surrounded by clear, shallow, undisturbed waters.

Diet:
They feed mainly on small and medium-sized fish, as well as the eggs and young of other birds, carrion, aquatic invertebrates such as crayfish, flying insects and earthworms.

Breeding:
Caspian terns can breed all year round, varying among different parts of their range. They breed most often in large colonies, often together with other terns, although they can also breed in smaller colonies or even in isolated pairs. Each pair nests on a shallow depression in sand or gravel, or sometimes on flat stone, where the female lays 2-3 buff-coloured eggs with dark spots and blotches. The eggs are incubated for 22-28 days and the chicks are able to leave the nest after a few days, but are fed by both parents until they fledge 35-45 days after hatching.

Conservation:
IUCN status - LC (Least Concern)
This species has a very large breeding range and the global population is estimated at 240.000-420.000 individuals. The overall population trend is increasing, although some populations are decreasing, stable, or have unknown trend. Population in North America have increased by 38% per decade over the last 4 decades.

Black tern

Chlidonias niger

Photo by Jari Peltomäki (Luonto Portti)

Common name:
black tern (en); gaivina-preta (pt); guifette noire (fr); fumarel común (es); trauerseeschwalbe (de)

Taxonomy:
Order Charadriiformes
Family Sternidae

Range:
This species breeds throughout most of Europe, western Asia and North America, as far north as Finland and the Northwest Territories of Canada and as far east as Kazakhstan and western Mongolia. They migrate south to winter along the western coast of Africa, along the coats of Central America and northern South America and along the Nile river.

Size:
These birds are 22-28 cm long and a wingspan of 56-65 cm. They weigh 50-75 g.

Habitat:
The black tern breeds in fresh or brackish water wetlands with dense vegetation and pockets of open water, such as marshes, lakes, slow-flowing rivers, ditches, swampy meadows, peat bogs or rice fields. Outside the breeding season they are mostly found in coastal habitats such as estuaries, saltmarshes and coastal lagoons, as well as marine water up to 600 km offshore, but also use some inland wetlands.

Diet:
They feed on small freshwater fishes, small molluscs, tadpoles and frogs, worms, crustaceans and insects such as damselflies, dragonflies, mayflies, grubs and various larvae. Outside the breeding season also small marine fish such as anchovies and silversides, and planktonic crustaceans.

Breeding:
Black terns breed in May-August. They nest in small colonies, each being made of dead water plants, either floating or on the ground very close to water. The female lays 2-4 light-brown eggs with large dark blotches, which are incubated by both parents for 19-23 days. The chicks leave the nest soon after hatching and are able to walk or swim in search of food, but only start flying 20-25 days after hatching. They reach sexual maturity at 2 years of age.

Conservation:
IUCN status - LC (Least Concern)
This species has a very large breeding range. Although there are no estimates of global population size, the black tern is considered widespread and relatively common. The population has undergone a decline both in Europe and North America, mainly due to habitat loss to drainage and agriculture, habitat degradation, human disturbance and reduced prey availability caused by pollution, pesticides, lake acidification and the introduction if exotic fishes. Overfishing may affect food availability in some wintering areas.

Royal tern

Sterna maxima

Photo by Ianaré Sévi (Wikipedia)

Common name:
royal tern (en); garajau-real (pt); sterne royale (fr); charrán real (es); königsseeschwalbe (de)

Taxonomy:
Order Charadriiformes
Family Sternidae

Range:
This species breeds along the coasts of West Africa, from Mauritania to Cameroon, along the Caribbean and the coasts of South America from Colombia no northern Brazil, and along the coasts of south-eastern Brazil, Uruguay and north-eastern Argentina. There is also a breeding population in the eastern United States along the coasts from North Carolina to Massachusetts Outside the breeding season they wander from Morocco to Angola, along Central America and the Gulf of Mexico, and also along the Pacific coast from Guatemala to northern Chile.

Size:
These birds are 42-50 cm long and have a wingspan of 125-135 cm. They weigh 350-450 g.

Habitat:
The royal tern is found in inshore waters, bays, lagoons, harbours, estuaries, saltmarshes, mudflats, sandflats and mangroves, preferring barren sandy beaches and coral islands to breed. They are only found in coastal areas, up to an altitude of 100 m.

Diet:
They mainly hunt on salt water, feeding on small fish, squids, shrimps and crabs.

Breeding:
Royal terns can breed all years round, varying between different parts of their range. They nest in large, dense colonies of up to several thousands of pairs, often in association with other terns and small gulls. They are monogamous and both sexes help build the nest, a shallow scrape on bare ground placed near the high tide line. There the female lays 1-2 eggs which are incubated by both sexes for 25-31 days. The chick may remain in the nest for up to 1 week, but eventually leaves to join the other chicks of the colony in a large crèche. While in the crèche they continue to be fed by their parents. They remain in the crèche until fledging, 28-35 days after hatching, but continue to rely on their parents for food and protection for 5-8 months.

Conservation:
IUCN status - LC (Least Concern)
This species has a large breeding range and the overall population trend is believed to be stable, although some population have an unknown trend and the population in North America have undergone a small increase over the last 4 decades.

Forster's tern

Sterna forsteri

Photo by Dick Daniels (Wikipedia)

Common name:
Forster's tern (en); andorinha-do-mar-de-Forster (pt); sterne de Forster (fr); charrán de Forster (es); Forsterseeschwalbe (de)

Taxonomy:
Order Charadriiformes
Family Sternidae

Range:
This species breeds in southern Canada and the northern United States, wintering in the south-eastern and coastal south-western United States, along the eastern and western coast of Mexico, in Central America and the Caribbean.

Size:
These birds are 33-36 cm long and have a wingspan of 64-70 cm. They weigh 130-190 g.

Habitat:
The Forster's tern breeds in freshwater lakes, potholes, inland and coastal marshes and occasionally on sand, mud or rocky islets. Outside the breeding season they are found foraging on lakes, streams and estuaries, favouring waters less than 1 m deep.

Diet:
They feed on small fish, crustaceans and aquatic insects.

Breeding:
Forster's terns breed in April-July. They form loose breeding colonies of 5-250 pairs. Both sexes build the nest, a small cup made of plant materials or a scrape on muddy or sandy soil, usually placed on a small islands, lakeside or among floating and emergent vegetation. The female lays 2-5 eggs which are incubated by both sexes for 23-25 days. The chicks are fed by both parents and fledge 3-4 weeks after hatching.

Conservation:
IUCN status - LC (Least Concern)
This species has a very large breeding range and a population estimated at 130.000-160.000 individuals. the population has undergone a small increase over the last 4 decades, but it may be vulnerable to habitat loss due to the degradation, development, draining, and filling or flooding of wetland habitats, as well as human disturbance.

Peruvian tern

Sternula lorata

(Photo from Internet Bird Collection)

Common name:

Peruvian tern (en); trinta-réis-do-Peru (pt); sterne du Pérou (fr); charrancito peruano (es); Peruseeschwalbe (de)

Taxonomy:

Order Charadriiformes

Family Sternidae

Range:

This South American species is restricted to the Humboldt Current zone from northern Peru to the Peninsula of Mejillones in Chile.

Size:

These birds are 22-24 cm long and weighs 45-60 g.

Habitat:

They breed either on broad sandy beaches and dunes associated with wetlands, or in desert plains, always within 3 km of the coast. They generally forage in shallow inshore areas, but occasionally seen 10-70 km offshore, and will also forage in coastal wetlands.

Diet:

They hunt fish by darting into the water, mostly taking anchovies Engraulis ringens, South Pacific sauris Scomberesox saurus, Peruvian silversides Odonthestes regia and mote sculpins Normanychtis crockeri.

Breeding:

Peruvian terns breed in October-January. They nest in small groups, with 3-25 pairs in loose aggregation. Each pair nests in a shallow depression on bare ground, where the female lays 1-2 buff-coloured eggs. The eggs are incubated by both parents for 22-23 days and the chicks leave the nest within 2 days after hatching. The parents will protect the chicks from predators until they fledge, 21-24 days after hatching.

Conservation:

IUCN status - EN (Endangered)

This species has a relatively small breeding range and a global population estimated at just 1.000-2.500 individuals. The population is suspected to be declining on the basis of continued destruction and degradation of its breeding habitat, disappearance of breeding colonies in the last 30 years and population decline in some localities. This species was gravely affected by the 1972 collapse of anchoveta Engraulis sp. stocks, but currently the main threat is the destruction of breeding habitat through the building of shanty towns, summer homes, road constructions and off-road recreational driving. Other threats include wetland pollution and water use for irrigation, conversion of desert plains into agricultural land, management of wetland water levels and oil exploration near breeding areas.

Inca tern

Larosterna inca

Common name:

Inca tern (en); andorinha-do-mar-Inca (pt); sterne Inca (fr); charrán Inca (es);

Inkaseeschwalbe (de)

Taxonomy:

Order Charadriiformes

Family Sternidae

Range:

Confined to the Pacific coast of South America, these birds breed in the coasts of Peru and Chile.

Size:

The Inca tern is a large tern, 40-42 cm long. Males and females are similar in size, with a wingspan of 60 cm and a weight of 220 g.

Habitat:

This species feeds in the cold waters of the Humboldt current. It breeds on inshore (and occasionally offshore) islands and rocky coastal cliffs.

Diet:

The Inca tern feeds by plunge diving for fish. Often in large flocks, they prey on schooling anchoveta Engraulis ringens, mote sculpins Normanychtic crokeri and silversides Odothestes regia. They also eat crustaceans and scavenge offal and scraps from sea-lions and fishing boats.

Breeding:

The Inca tern nests in a hollow or burrow, or sometimes the old nest of a Humboldt penguin Spheniscus humboldti, and lays one or two eggs. The two main peaks of egg-laying occur in April-May and October. The eggs are incubated for about 4 weeks, and the chicks leave the nest after 7 weeks.

Conservation:

IUCN status – NT (Near-threatened)

Although still common in many locations, the current population of 150.000 is much lower than in the past. Recent phenomena of El Niño Southern Oscillation (ENSO) have caused mass breeding failure. The guano industry and overfishing of their prey are the two main threats on this species.