The Chiffchaff and Willow Warbler are nearly identical in appearance, but are easily separated by their songs.
Chiffchaff (Apr, Herts).
Willow Warbler (May, Cumbria).
The third Phylloscopus warbler, the Wood Warbler, has two different song types (June, Suffolk).
The Blackcap and Garden Warbler are closely related species. The Blackcap song usually begins with scratchy notes that transform into a rich melody, whereas the Garden Warbler is a sustained rich warble.
Blackcap (May, Herts).
This more sustained song has a blackbird imitation (25s), and resolves at the end with the sweeter notes typical of Blackcap. I listen for these notes to separate the song from the similar Garden Warbler (May, Herts).
Garden Warbler (May, Herts).
The Grasshopper Warbler song is a continuous reeling sound and often heard at night. The intensity varies as the bird turns its head (May, Herts).
Lesser Whitethroat (May, Herts).
The Sedge Warbler song differs from the similar Reed Warbler song in its frequent changes in pace and greater degree of mimicry (June, Herts).
Cetti's Warbler has an explosive song uttered from a bird hidden in marsh vegetation. There is a considerable time interval between phrases.
(6.00am, Apr, Suffolk)
Except for Chiffchaff and Cetti's Warbler, the above were recorded in 1978 and 1979 and have been digitised from cassette tape.
Chiffchaff alarm call (Apr, Herts). The Willow Warbler call is more bisyllabic.
Blackcap alarm call (Apr, Norfolk).