Chiffchaffs

Last year (2019), my first singing Chiffchaff of the year was in late February at Great Melton, Norfolk, not surprising given the exceptionally mild conditions and favourable winds.
I have heard from others that Chiffchaffs were encountered in the first few days of March, however, I recorded my first rather later on the 11th of March.
At the time of writing, Chiffchaffs are now well established on their breeding grounds with good numbers seen and heard at many sites.

Chiffchaff at Great Melton, Norfolk, 22nd March

Chiffchaff Great Melton, Norfolk 22nd March

Chiffchaffs are easily separated from their close relative, the Willow Warbler, in both appearance and behaviour.  Primary projection is always a feature to check, here, you can see the primaries extend little beyond the secondaries whilst on Willow Warbler the primaries extend further beyond the secondaries, indicating the greater journey of the migrant.
The Chiffchaff has a habit of a frequent downward movement of its tail, Willow Warblers may only do this once, or never.
Song can be interestingly, I have encountered a few Willow Warblers which have opened a verse of song with the Chiffchaff "chiff-chiff-chaff-chiff-chaff" before breaking into its own song, a case of mimicry perhaps.