Phylloscopus trochilus

Willow Warbler

Main author: Magnus Hellström, September 2014.
Citation: Ottenby Bird Observatory. 2015. Ringers’ DigiGuide – Phylloscopus trochilus. www.ringersdigiguide.ottenby.se

MOULT

                     Adult         Young

Summer       SC              sp

Winter          WC            WC

Young sp: The post-juvenile moult includes most of body and often (but not always) LC and MC. According to Jenni & Winkler (1994) 17% include inner GC, but only rarely more than GC10, and occasionally also single TT and RR.
Young WC: The pre-breeding moult includes whole plumage. A few spring birds show single feathers in better condition, but this is likely to reflect prolonged moult periods during winter. Rare occasions of single ’forgotten’ feathers are know. 
Adult SC: The post-breeding moult includes whole plumage. According to Jenni & Winkler(1994) 4% seem to retain single inner SS or single LC. 
Adult WC: The pre-breeding moult includes whole plumage. A few spring birds show single feathers in better condition, but this is likely to reflect prolonged moult periods. Rare occasions of single ’forgotten’ feathers are know. 

SEX:

No plumage differences.

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