It’s a good idea to put a bait hive or swarm trap up in the spring. This has a two-fold purpose, firstly you might catch a passing swarm, secondly if one of your own hives swarm you might catch the swarm rather than seeing it disappear either into the distance, or into some less convenient location such as under your shed.
These swarm traps are available from beekeeping equipment suppliers, but you can create your own. I have used a nuc box very successfully, with a drawn frame or just foundation if you have no drawn comb. You can purchase small vials of pheromone, the swarm lures are supplied with one vial. I’ve tried these without much success, I like to put a few drops of lemon grass oil instead, bought from a local health food store. The bees seem to like this at least as well as the pheromone, I place this box about 8 feet off the ground facing east or south east.
I once had a call from someone who had a few bees flying around ever opening on one side of his house. There was a roof vent, bathroom vent, kitchen fan and air conditioning vent, each one had about a dozen bees trying to get in. He had already had bees in his roof and didn’t want them again. I wondered for a few minutes, then a light bulb went on in my head, I should use a swarm trap. I got a hive box with some comb inside and put it on top of his patio cover, which was about 8 feet off the ground, facing east. That was about 4 o’clock in the afternoon, he called me at about 8.30 the next morning to tell me the box was jammed full of bees.
What we had seen were scout bees from a swarm hanging nearby, I just presented them with a location which was much more attractive to them than any of the other options, and they moved right in.
Another time I went out to my truck to go on a bee swarm call, there were more bees than usual flying around the back of my truck. The bees had found an empty hive, which I was going to use for the swarm collection, and had taken it for their own. It doesn’t get much easier than that. Of course as with collecting a swarm, you don’t know what these bees will be like, but since the cost and effort you’re spending is almost zero it seems like good value to me.