Willow Warbler: mixed singer Barton April 17th 2021

Initially I heard this strange phylloscopus warble song this morning just before dawn. It had a bit of Iberian Chiffchaff about its structure but was clearly not right for that species. When seen well the bird was very bright and clearly looked like a Willow Warbler. Later in the morning it began to include more Willow Warbler phrases in its song and eventually reverted to pure Willow Warbler at times. The recordings, below, are very similar to some on xeno-canto that are logged as Willow Warbler, mixed singers.