Willow warbler feeding

[ADAM PHILLIPS]

I was watching a willow warbler this morning , it was in a blackthorn tree about 6 feet above me and it was hopping about  looking for bugs to eat.
Then I realised it wasn't picking bugs it was going from flower to flower and appeared to be feeding on the flowers like a humming bird, but perched , not flying.
Is this something they do or am I mistaken?
I am certain that's what it was doing.