White-winged Tern
The white-winged tern (Chlidonias leucopterus), also known as the white-winged black tern, is a small, elegant member of the Laridae family. Unlike many of its relatives that frequent salty coastlines, this species is primarily associated with freshwater environments. Its genus name, Chlidonias, is derived from the Ancient Greek word khelidonios, meaning "swallow-like," a nod to its graceful flight and physical appearance.
While "white-winged tern" is the standard name in most English-speaking regions and the preferred term for formal ornithological authorities in the United Kingdom, the name "white-winged black tern" remains common in popular usage.
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Key Facts
- Scientific Name: Chlidonias leucopterus
- Conservation Status: Least Concern (IUCN 3.1)
- Primary Habitat: Freshwater marshes and bodies of water.
- Diet: Primarily insects and small fish.
- Distribution: Europe, Africa, Asia, and Australia.
- Distinctive Feature: White wings contrasting with a dark body during breeding season.
Physical Description
Breeding Plumage
During the summer, adult white-winged terns exhibit a striking appearance. They possess a black neck and belly, a very dark grey back, and a white rump. Their wings are predominantly white, though the inner wing is grayish with brown-tipped coverts. The tail is light grey, appearing almost white, and the face is tinged with yellow. Their bills are small, stubby, and black, measuring between 22–25 mm, and their legs are short and red.
Non-breeding and Juvenile Plumage
In the non-breeding season, the bold black coloration is largely replaced by white or pale grey. The head remains black with a white forehead, and the crown is blackish-brown with white flecking. A distinctive dark triangular patch is visible forward of the eye, complemented by a broad white collar. Juveniles and moulting adults often feature a pale grey rump and a dark brown "saddle" across the mantle, with feathers tipped in a paler brown.
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Distribution and Habitat
The white-winged tern is a global traveler with a preference for freshwater marshes. Its breeding grounds extend from southeast Europe through Central Asia to the Russian Far East. In these regions, they build nests from small reed stems and other vegetation, placing them either on the ground near water or on floating vegetation. Typically, a clutch consists of 2–4 eggs.
During the winter, these birds migrate to southern Asia, Australia, and Africa. While not native to the Americas, they are recorded as scarce vagrants (birds that wander outside their normal range) along the Atlantic coast of North America, with occasional sightings in the Great Lakes area and on the Pacific coast. They have also been spotted in South American countries, including Brazil, Argentina, Uruguay, and Colombia.
Behavior and Ecology
The white-winged tern belongs to the group of "marsh" terns. Unlike "white" terns (genus Sterna), which dive deep into the water for prey, Chlidonias leucopterus employs a surface-picking technique. They fly slowly and leisurely over the water, snatching insects from the air or picking small fish from the surface.
Due to its migratory nature, the species is protected under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA), an international treaty designed to conserve migratory waterbirds throughout their flyways.
Hybridization
There are documented instances of hybridization between the white-winged tern and the black tern. Such hybrids have been recorded in the Netherlands and Sweden. In England, juvenile birds found at Chew Valley Lake in 1978 and 1981 were believed to be hybrids, displaying a mix of characteristics: the dark mantle of the white-winged tern combined with the dark breast patches typical of the black tern.
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Species Summary
| Feature | Details |
|---|---|
| Family | Laridae |
| Average Bill Length | 22–25 mm |
| Clutch Size | 2–4 eggs |
| Feeding Style | Surface-picking and aerial insect hunting |
| Conservation Status | Least Concern |
Frequently Asked Questions
How does the white-winged tern differ from other terns in its hunting style?
Unlike the "white" terns that dive for fish, the white-winged tern is a "marsh" tern that flies slowly over the water to pick items from the surface or catch insects in mid-air.
Where does the white-winged tern breed?
They breed in freshwater marshes ranging from southeast Europe to Central Asia and the Russian Far East, nesting on the ground or on floating vegetation.
What is the difference between its summer and winter plumage?
In summer, adults have a striking black neck and belly with white wings. In winter, most of the black is replaced by white or pale grey, though some blackish feathers and a black head with a white forehead remain.
Is the white-winged tern an endangered species?
No, the species is currently classified as "Least Concern" by the IUCN (version 3.1).
Can white-winged terns be found in the Americas?
Yes, but only as scarce vagrants. They have been recorded on the Atlantic and Pacific coasts of North America, as well as in South American countries like Brazil and Colombia.