Black-headed Gull Chroicocephalus ridibundus

(last update: 19-03-2014)

Black-headed Gull - 2cy July

This section deals with second-calendar year Black-headed Gulls in the month of July.

Introduction

In July, second-calendar year Black-headed Gulls are undergoing a complete moult into ’adult winter plumage’. This second winter plumage is adult like but a small minority of gulls can be distinguished as ‘second winter plumage’ from 2cy August-3cy February by dark markings on tertials, outer primary coverts and alula.

Moulting into second winter has started in June, usually 3-4 weeks earlier than in adults. Most Black-headed Gulls are in coimplete winter plumage from mid-August:

• Head from early June, majority have winterhead mid-July;
• Primary-moult slower than in adult
• P1: mid may- early July
• P3-4: mid-July
• P5-7: late July
• P9-10: mid-July- late August
• Secondaries: June-late July, starting when primary moult has reached around P5
• Median coverts: late July- mid August
• Tail: late June- August

Adult winter plumage is characterized as follows:   

• Head: white with dark ear spots and traces of vertical bars above eyes. Moult of head starts with forehead, developing backwards.
• Hindneck and underbody: white
• Bare parts: bill deep red with dark tip, legs dark reddish, iris dark brown
• Upperwing ‘tricoloured’:
• p7-p10: white (with black edge of outer web not reaching tip on p10)
• p5-p10: black-tipped, extending on to inner edge of inner web
• p4-p7: with white extreme tip
• p1-p6: grey with blackish-grey innerwebs on p1-p5
• secondaries: grey with white tips
• Underwing: outer primaries white, dark tipped, mid primaries dark
• Tail: all white

Most of the description follows: 
P.J. Grant: "Gulls, a guide to identification".
K.M.Olsen: “Gulls of Europe, Asia and North America”.