Gull billed Tern and the Australian Tern

The bird in the foreground is an uncommon bird here in Australia and was a lifer for me today! [15/03/2020] It is a Gull billed Tern.

From Wikipedia; The Gull-billed Tern (Gelochelidon nilotica), formerly Sterna nilotica, is a tern in the family Laridae. The genus name is from Ancient Greek gelao, "to laugh", and khelidon, "swallow". 

Specifically the bird pictured is of the Asian sub specie affinis which is found in Transbaikalia to Manchuria, Japan, south and east China through southeast Asia to the Philippines, Borneo, Sulawesi & Sumatra.

The Australian Tern (Gelochelidon macrotarsa), also pictured above but in the background, was previously considered a subspecies of the Gull billed.

The above picture shows both species in non breeding plumage so it is reasonable to compare the birds so as to emphasise the differences. The Australian Tern is beginning to moult into breeding plumage.

close up of affinis facial pattern

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The Gull billed [affinis] is 

• smaller, 
• thinner [and straighter] billed, 
• different face pattern - less black behind eye, 
• overall dark patch is smaller and lighter in colour, 
• dark patch is broken by a partial white eye 'ring' especially around the bottom of the eye, 
• lores are much paler, 
• legs seem a little paler [am i making that bit up???], 
• back and wings seem a little greyer / darker than the Australian Tern,
• shorter legged 

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