About Gelochelidon macrotarsa (Gould, 1837)
Gelochelidon macrotarsa (Gould, 1837) is a fairly large, powerful tern that is similar in size and general appearance to the Sandwich tern, but can be distinguished by its short thick gull-like bill, broad wings, long legs, and robust body. Adult breeding (summer) individuals have pale grey upperparts, white underparts, a black cap, a solid black bill, and black legs. Their characteristic call is described as ker-wik. This species measures 33–42 cm (13–17 in) in total length, has a wingspan of 76–91 cm (30–36 in), and weighs between 150–292 g (5.3–10.3 oz). It differs from the closely related gull-billed tern by being slightly larger, having paler grey upperparts, and possessing an obviously larger, heavier bill. In the non-breeding (winter) season, adults lose their full black cap and develop a dark patch through the eye, similar to the pattern seen on Forster's terns or Mediterranean gulls. Juvenile Australian terns have a fainter mask than winter adults, but otherwise closely resemble winter adult plumage. This tern breeds in Australia; some individuals migrate to New Guinea during the non-breeding season.
