Bees collecting pollen to feed the brood

We haven't dared open the hive up to check them, but judging by the amount of pollen they are collecting, this lot must be building up a lot of brood. Today we observed 3 slightly different shades of yellow pollen and one very pale buff/cream. The main quantity is a day-glow bright yellow which I think must be from willow cat-kins where we have heard them buzzing.

Anyway - check out the video and seen them whizzing in and out of the hive.