Mystery Bird: White Tern, Gygis alba

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[Mystery bird] The White Tern is known by more alternate names than a con-artist, also being known as the Angel Tern, Common White-tern, Common White Tern, Little White Tern, Little Fairy Tern, Fairy Tern, Little White-tern, Little Fairy-tern, and even (since it lives in tropical oceans of the world) as the Atlantic White Tern, Gygis alba (formerly; Gygis microrhyncha), photographed on Midway Atoll National Wildlife Refuge -- one of the most remote coral atolls on earth -- a US territory in the north Pacific Ocean [I will identify this bird for you in 48 hours]

Image: Joe Fuhrman, 2010. [larger view] I encourage you to purchase images from this professional photographer.

NOTE: Please name at least one field mark that supports your identification.

This wide-ranging and stunningly beautiful mystery bird is famous for a unique and astonishing behavior -- what is this behavior?

This small tern is famous for laying its egg on bare thin branches in a small fork or depression of a tree or bush. This balancing act is probably a predator-avoidance behavior as the branches they choose are too small for rats or even small lizards to climb (although I was intrigued by several commenters' observation that this is a way to avoid insect/arachnid nest parasites). White Terns are also quick to relay should they lose the egg in a windstorm. Newly hatched chicks have well developed feet that they use to hang on to their precarious "nest."

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These are Good Terns, because there are two together.

They lay their eggs in trees, but make no nest for them. This might seem insecure, but may help reduce intranest ectoparasitism.

Actually, I don't know how to separate this lovely species from the SW Pacific bird which sometimes shares the same common name, but falls into an entirely different genus; the stated location was my clue for the ID.

BTW, I love this photograph!

By Pete Moulton (not verified) on 16 Jul 2010 #permalink

Great post, Pete, but I think intranest ecoparasitism is handled by laying only one egg :-)

If my ID is correct (i am frequently wrong so take this with a grain of salt), I've read that they can regurgitate their stomach oil onto predators - now that is cool behavior.

Thank you, Patty. Theye guys are colonial breeders, so I'd expect parasitism to be an issue for them, especially if their breeding potential is so low.

As to the regurgitation of the stomach oils on predators, I knew fulmars (both kinds) have an evil reputation for that habit, and in fact 'fulmar' itself is a reference to it. I've never heard of that behavior among these guys.

By Pete Moulton (not verified) on 16 Jul 2010 #permalink

Do fulmars do that too? See, I was thinking Oceanodroma furcata, based upon the tail shape. But as i look at the bill shape, i see you are right on the type of Tern that lays its eggs in tree branches sans nest. Fascinating!

And the Good Tern pun was excellent :-)

Thank you again, Patty. I won't claim the pun, but learned it many years ago during college (How many years? It was inscribed on a clay tablet,IIRC). Your thought of O.furcata never even occurred to me, though it sure should've.

Yes, fulmars are well known for that habit. I've read that the word 'fulmar' comes from the Norse, and means 'foul gull', which most people who care about such things seem to think refers explicitly to it.

By Pete Moulton (not verified) on 16 Jul 2010 #permalink

Well, at least you had clay, so you're not older than dirt :-)

They're called Manu-o-ku here in Hawaii. Black-tipped bills with a bluish base. The eye-ring makes them look all doe-eyed :)

If you guys didn't know, while common in the NWHI, they also breed in one other location in the entire Hawaiian chain. Surprisingly it's not one of the less populated islands or a remote state park. Manu-o-ku breed in Honolulu. And not in the outskirts either. Right in the heart of town.

I work in a grimey building in chinatown, listening to the sounds of the city. All the while pairs of them fly overhead, unconcerned. It's a cool juxtaposition.

Awesome photo btw!

By Sebastian Marquez (not verified) on 16 Jul 2010 #permalink