Reading the signs

Long before a swarm leaves, the colony tells you what it is planning:

• Bearding, a mat of bees clustered on the front of the box even in modest heat, is the least specific sign, since a crowded but contented colony beards too, but paired with anything else here it earns a closer look
• Backfilling shows as nectar packed into cells at the edges of the brood nest, squeezing the pattern smaller than it should be for the season
• the queen herself often slims down in the days before departure, workers reducing her feeding so she can fly
• on the morning a swarm actually issues, the entrance frequently goes quiet first, foraging traffic dropping off before the roar starts, as though the colony were gathering itself

None of these signs alone is proof, but together they are a colony announcing its plans out loud.