some times but from your photo, i would guess not, from my mentor, he says usually if they are going to swarm, they will make a loud humming sound, kinda like they are being disturbed. kinda like the sound they make when you do an inspection of the hive, when they are in a good mood and working hard they make a calm soothing humming noise, but when they are disturbed they pick up the humming to a higher level, this is what to listen for, but in your case i wouldn't worry right now. another way to check is to do an inspection of the lower brood box, check for queen cells hanging on the outside of the frames, they will be very noticeable, kinda long and hanging, very distinct looking form the rest of the brood.