Gull ID

[Cardinal15]

Found this gull at Lake Rotoma on the 1/3/20. It was with similar-looking gulls. Differences were distinctive yellow legs and a more yellow bill compared to the surrounding gulls, and sleeker body. It was also the first gull to fly when approached. This gull also had a significantly different bill.

[Davidthomas]

Looks like a fledgling black-billed gull to me, longer finer Bill, slighter Bird overall and a more round head compared to the juvenile redbilled gull which has a much chunkier shorter bill

[Finn Davey]

Juvenile Black-billed gull.
Much longer and thinner bill, much more pale coloured than the Red-billed juvenile next to it and no/less brown spots on wings.

[Clinton9]

See this...

Black-billed gull-paler grey back and longer thinner black beak
Red-billed gull-darker grey back and shorter thicker red beak

Whitey (1).jpg (571.82 KiB) Viewed 2084 times

[Finn Davey]

Got the wrong genus there.
Red-billed Gulls and Black-billed Gulls are no longer in the genus Larus, they're in the genus Chroicocephalus now and have been for a while.

You'll also notice that Black-billed gulls have less black on their wing tips, the black is at the very edge while Red-billed Gulls have an entirely black wing tip.

Black-billed Gulls also have smaller pupils, this is noticeable in adult birds.

[simon.fordham]

As always, Finn, this depends on which taxonomical reference you choose.

There is no single international standard. IOC use Chroicocephalus but NZ Birds Online and Birdlife International both use Larus.

Simon

[Oscar Thomas]

I will also mention that pupil size is not a defining characteristic for most (if not all) bird species as it is constantly regulated and changing. Black-billed Gulls can have smaller or larger pupils as a response to light intensity, but there are also some species that alter their pupil size as a display technique.

[Cardinal15]

Thank you. Much appreciated. I just got a bit confused with the yellow legs.