Gull-billed Tern Identification Guide

Overview

The Gull-billed Tern (Gelochelidon nilotica) is a distinctive, wide-ranging tern found on coasts and inland wetlands across much of the world. Unlike most terns, it feeds heavily on insects and small terrestrial prey caught on the wing or picked from the ground, rather than diving for fish.

Key Field Marks

• Size and shape: Medium-sized, stocky tern about 33-38 cm (13-15 in) long with broad-based wings, a relatively short, only moderately forked tail, and a heavy-bodied build compared to slimmer "sea terns."
• Bill: Short, thick, and entirely black — noticeably stubbier and gull-like compared to the long, slender, often red or orange bills of many other terns, giving the species its name.
• Plumage: Pale gray upperparts and white underparts; breeding adults have a full black cap, while nonbreeding and juvenile birds show a whitish head with a dark smudge through and behind the eye.
• Legs: Black legs, longer than in many terns, suited to its habit of walking and foraging on the ground.
• Flight and behavior: Flies with buoyant, gull-like wingbeats; frequently hawks insects in flight like a giant swallow, hovers briefly, and forages over fields, marshes, and mudflats as often as open water.

Separating It from Similar Species

• Common and Forster's Terns: Both have longer, thinner, orange-to-red bills (often with a black tip) and more deeply forked tails; Gull-billed's stout all-black bill is the best distinguishing feature.
• Sandwich Tern: Has a long, slender black bill with a yellow tip and a shaggy crest, quite different from Gull-billed's short thick bill.
• Caspian Tern: Much larger with a massive red-orange bill, easily separated by size and bill color alone.

Habitat, Range, and Season

Breeds locally on sandy or shelly coastal beaches, barrier islands, and salt marshes, as well as inland at lakes, salt flats, and agricultural wetlands across scattered populations in North America, Europe, Africa, Asia, and Australia. Northern populations are migratory, wintering along tropical and subtropical coasts; many populations elsewhere are resident or make shorter movements. Look for it over marshes, plowed fields, and mudflats as much as beaches, especially during the breeding season.

Voice

Gives a distinctive nasal, laughing "ka-way" or "kay-wek" call, harsher and more rasping than the higher-pitched calls of Common or Forster's Terns, often given in flight.