I often see small birds like these pecking away at dead bees around my hives in the winter.
It doesn’t seem to take long for the birds to realise where the bees are.
Usually see the birds swoop down from the trees, flitter from one bottom entrance to another, grab a bee and fly back up in the trees to eat it.
In this case the bird flew to the top of a hive instead. According to the University of Delaware (PDF):
“Various types of birds such as shrikes, titmice, kingbirds, swifts, martins, thrushes, mockingbirds and others may eat honey bees. They consume very few bees and most bee colonies can suffer the occasional loss of a worker bee to a bird.”
It’s never been a problem for me.