Abit about Wing Moult in first winter gulls

Hopefully readers will find this post useful. Understanding wing covert pattern and the advance of wing moult was a real turning point for me learning about gulls and a really important bit of information for identifying first winter Gulls especially.

Yellow Legged Gull numbers are continuing to drop here on the inner London Thames however a few 1st winters and an adult were lurking about on Sunday morning. Below are the 1cy birds showing wing, and in the case of the second bird, tertial moult.

ylg

_mg_0064

Wing moult, (shown above as the darker, diamond shaped, white fringed replaced feathers dotted amongst the first generation coverts in the wing) combined with other supporting features is a reliable method for separating 1st winter Yellow Legged and Caspian from Herring and Lesser Black backed Gulls. Supposedly caused by the former two species being born in a warmer climate with earlier breeding season and therefore an older bird by the time we see it here in autumn/winter.

Up until last month I had not heard of 1cy Herring or Lesser Black-backed gulls having replaced wing coverts before spring. The bird pictured below however , photographed in Regents Park London by Dante Shepherd this October, contradicts the rule and has included c40% of its wing coverts in its post juvenile moult.  These replaced feathers are less heavily marked than Yellow in Legged gull, with a pattern recalling 2nd generation Herring gull- type scapulars rather than the seemingly dark centered diamond headed coverts of YLG.

advanced-1cy-herring

advanced-herring-flight

Flight shot shows tail pattern and large window in the inner primaries, revealing the ID of this interesting bird.

N.B: It should also be said that if a bird doesn’t show any wing moult in its post juvenile plumage it could still be a Yellow-Legged or Caspian Gull, and this method should be used carefully in combination with other features.

One thought on “Abit about Wing Moult in first winter gulls”

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s