A not particularly amazing picture of a Chiffchaff.......
Similar to a Willow Warbler but.......
Chiffchaff usually arrive first (willows in next couple of weeks)
Darker legs (not always some willow legs can be darker)
More greenish/dark (willow tends to be more yellowy)
Less significant eye stripe (not always very obvious)
Shorter "wings" (Primaries are short and stubby - willow longer to reflect its longer migration)
Different calls - not going to describe them though.
Here endeth the lesson.
Gulls are also establishing partners and sorting out old battles