bees are bearding, some call it feastoning, but i'm not sure feastoning is the same (i think this term goes for the mode, when they produce wax)
anyway, they are bearding outside the hive, nothing bad about it, the ammount i see is nothing to be worried about.
this is caused by multiple things, the hive has grown to the extent, that there are too many bees to fit inside at the same time as to keep the temperature right-if they all went inside, it would be too hot.
many will suggest you using a top entrance, which improves ventilations thus keeping better temps etc etc, much has been said about it, anyway not to be worried
if there was this much bees--->
i would be getting worried