jezd,
i would imagine they took a big hit this winter
A cold winter will harm them no more, and probably a lot less, than a well provisioned bee colony.
I am just surprised that it is warm enough for them to be out of hibernation yet. They are still tucked up tight in their winter quarters around here, as are the bumbles. Not seen any yet and don't expect them to emerge from hibernation until the weather improves by a few degrees yet. Bees flying in the sunshine, but still not warm by any stroke of the imagination. I reckon people are measuring the temperature out in the sun, not the shade temperatures - or I am living in a cold pocket of the UK!
Regards, RAB