coverts. The buffish yellow pervading the whole of the autumn plumage 
is never entirely lost by abrasion in winter. 
The Chiffchaff may be distinguished from the Willow-Warbler by its 
wing-formula. In the present species the second primary is intermediate 
in length between the sixth and ninth; whilst in the Willow- Warbler it 
is almost invariably between the fifth and sixth. A further distinction 
may be found in the almost black legs of the present bird and its browner 
plumage. 
440 BRITISH BIRDS. 
