RSPB Pulborough Brooks. Notoriously tricky to ID because they are so similar to Chiffchaffs. However, the latter being a short-distance flyer has short primary wing projections, making the wings look dumpy. In addition, Chiffchaffs don't have such a strongly defined supercilium and have quite an obviously eye ring. Although books say Chiffchaffs are supposed to have dark legs and Willow Warblers pink, that is not always a very reliable ID feature. So you have to take a bunch of features for ID.

Willow Warbler (Phylloscopus trochilus) (04/05/2008) RSPB Pulborough Brooks. Notoriously tricky to ID because they are so similar to Chiffchaffs. However, the latter being a short-distance flyer has short primary wing projections, making the wings look dumpy. In addition, Chiffchaffs don't have such a strongly defined supercilium and have quite an obviously eye ring. Although books say Chiffchaffs are supposed to have dark legs and Willow Warblers pink, that is not always a very reliable ID feature. So you have to take a bunch of features for ID.

Willow Warbler (Phylloscopus trochilus) (04/05/2008) RSPB Pulborough Brooks. Males and females alike so tricky to distinguish.

Willow Warbler (Phylloscopus trochilus) (04/05/2008) RSPB Pulborough Brooks.

Willow Warbler (Phylloscopus trochilus) (05/05/2008) RSPB Pulborough Brooks.

Willow Warbler (Phylloscopus trochilus) (17/06/2007) RSPB Pulborough Brooks.