Colony 1 has been continuously occupied for over 6 years. Every spring, except 2018, there have been bees crawling around outside the hive -- stricken with Deformed Wing Virus or some other paralysing virus. These bees became food for Sparrows.
This year seems worse than previous years. There appear to be more bees crawling and for longer. This might not be worse than usual but it feels it. In April it was mostly Drones which were crawling around. Now it is more likely to be workers.
Last season had a very cold spring. Four out of seven colonies died from starvation or isolation starvation (ie there were too few bees to reach the few stores that were left). There was a definite brood break which will have reduced the number of Varroa and may have been the reason that there were very few crawling bees that season. Observing crawling bees is confused by the Sparrows eating them. I think that in 2018 there was very little Sparrow activity.
This season there have been warmer temperature. I can't say for sure whether there was a brood break. There have been higher than expected levels of Varroa this season which suggests that any brood break that did happen had a limited effect on Varroa numbers.
All this points to higher stress in the established hives this season. Conventional wisdom would suggest that there will be colony failures. Perhaps this will happen. I would expect that this would be seen as colonies succumbing to robbing by wasps or other colonies if it does. We'll see what happens.