The bees were collecting pollen and nectar. Snowdrop pollen is orange and some of the pollen baskets were loaded. The bees spend a lot of time grooming the pollen and can hang on to a flower with one leg while doing so. They seem to clean their tongues with their front legs in flight after leaving a flower, as shown in the next two photos.
There are quite a lot of snowdrops in the garden - probably covering about 100 sq metres in the wood - and with the cold windy weather we have had all year so far I was worried the flowers would be over before the bees got out to them.