Re: Estimating the population of a hive
You can't exptrapolate anything about the population of a colony by the activity at the entrance. Usually on counts frames of brood covered in bees and forms and estimate or assesment of strength (not an actual number per se, simply weak, moderately strong, strong) of population and then whether there is enough honey stored to maintain that colony.
I disagree w/ the term grumpy used to describe activity at the entrance. Certainly active. Apparently a warm and sunny day. Probably at the peak of flight that day? When did you take that video? I noticed the drones, but they seemed to me to be exiting the hive on their own, not being ejected. Besides, it's way too early for that to be happening here in the Notheast.
Squeak Creek Apiaries