We spent the past couple of days at Draycote with the Juvenile Yellow-legged Gulls both me and Dave struggle with the Juveniles so it had been a learning curve for us both and very enjoyable I could spend everyday learning like this, but it is not every day you get such close views to be able to see the differences.
With the Help of Books and Tim Marlow who has been a very good teacher he explains everything so well in person and on his blog - http://www.rainsbrooknaturalhistory.com he goes through all the key points and the differences between yellow-legged, Lesser-Black Backed and Herring gull.
The main differences that have really struck me are, The much whiter face with dark eye mask, and the Bill is black with a more thick tipped end. Tertials with solid dark centres and pale edges and on some slightly oak-leafed at the tips only whereas in Herring Gull the Oak-leafed is more pronounced and in Lesser Black-backed there's usually none at all.
Mantle and scapulars dark brown with pale edges creating scaly pattern.
Also the Breast and flanks of Yellow-legged Gull is Brown-mottled but belly and central undertail - coverts pale and the legs are more of a fleshy light pink color and longer legged.
Yellow-legged Gulls tend to molt before Herring Gull and Lesser Black-backed Gull.
Yellow-legged Gull (Juvenile)
Yellow-legged Gull (Juvenile)
Yellow-legged Gull (Juvenile)
Herring Gull (Juvenile) with Yellow-legged Gull (Juvenile)
Lesser Black-backed Gull (Juvenile)
Yellow-legged Gulls (Juvenile)
Yellow-legged Gull (Juvenile)
In flight the Pale window on the inner primaries is less obvious than on Herring Gull but much more obvious than on Lesser black-backed Gull.
The Underwing coverts are dark brown more like Lesser black-backed than Herring Gull.
Yellow-legged Gull (Juvenile)
Lesser Black-backed Gull (Juvenile)
Yellow-legged Gull (Juvenile)
Lesser Black-backed and Yellow-legged flying off
