Where are all the Bluetits this year?

I live in the West Heath suburb of Birmingham, and in recent years I've become used to seeing a variety of birds in the garden: Bluetits mostly, also Great Tits, Robins, Dunnocks. Less frequently Long-Tailed Tits, Nut-Hatches and occasionally Coal Tits, Tree Creepers and Wood Peckers.

Two years ago I had Bluetits using my nest box. This year the same box has been used by a pair of Great Tits, and it has occurred to me that I haven't actually noticed many birds except, Coal Tits and Robins, plus the inevitable Wood Pigeons and pesky Magpies.

Has anyone else noticed the same thing? I'm wondering if the prolonged spell of dry weather we've had has affected the number of caterpillars available to feed on.