I think that what you have seen are workers.
Let me explain why .....
In the past I’ve seen smallish Common Carder bees with yellow fluff on their face and made the assumption that they were drones (males).
At the time it was late summer and there could have been drones about foraging.
These bees were working Himalayan Balsam flowers, so it is quite easy to catch the bee in your fingers to take a closer look at it when it backs out of the flower, to move on - and as males can’t sting, such a process would be quite safe too.
So, I caught one of these yellow faced bees when it backed out of a flower and was surprised that it stung me - the cheeky thing !
And the sting meant that the little blighter was a girl, not a boy !
(As I’m a beekeeper of many years experience, I’m not really worried about getting the odd sting.)
I’ve been much more circumspect at handling what I think are male carder bees since this incident !
But catching male White tailed bees (B. lucorum) in your fingers is much more certain and very safe.
I hope this helps ! Yours Clive
the carders are tricksy!
In many common species yellow faces are indeed a sign of a male bumblebee as you have rightly pointed out.
But with carders it isn’t a reliable sign of the males I’m afraid.
So be careful as Clive has said.
Male common carder bees do tend to be brighter and fluffier almost than the girls, but you can only reliably identify males by looking for lack of pollen baskets, longer curved antennae and a more blunt end to the abdomen.
Behaviour should be a clue too, because males never collect pollen and are therefore more leisurely than the females,
Thank you Clive and Elaine - that was very helpful and means, for you Elaine, that I can now send you my beewalk report!