Freebees

Well in the UK it is approaching that time of year when colonies may swarm. This starts in earnest in April and can continue until the end of July. In my area June is the month where it all happens. Swarms are the natural reproductive unit of a colony and are ready, willing, and able to develop a new colony. I will not discuss here the biology of a swarm only how to catch them!
Every year there is post after post of different forums about how to catch yourself a swarm so I thought I would save my keyboard the wear and tear and put it in one place.
Swarm trap or bait hive.
A minor distinction but for me a bait hive is a small hive that can function as such. A swarm trap will give the swarm a temporary location but quickly needs moving to a hive. Any move you make of a swarm prior to brood being present may lead to them absconding. Where possible I recommend using a bait hive. If you have empty hives it is all worth baiting them for swarms just in case.

 

Flower pot bait hive on the roof of Brinscall hall.

Warré style - two warré boxes with the bars not in the bottom box. I recommend a flat roof for ease of movement. You must be sure the floor, boxes, and roof stay together so clips and/or reliable hive straps are a must.
National style - a single brood box is sufficent again with a simple roof and all components well secured.
TBH style - This is much easier equipment wise as any container that will recieve approx. 8-12 topbars can be a perfectly good bait hive. I have made these from polystyrene shipping boxes and plant pots. The fact that the top bars can be removed and placed in a hive with the bees in-situ is very handy. I would say that it doesn't take much longer to make a bait hive that works well as a nucleus hive for splits, transport, or mating. Do NOT forget if you intend to leave the bees in there for more than a week to have a follower board or spacer bar so you can still manipulate the bars.

15 bar Topbar bait hive/nuc made from old shipping pallets.

So to the matter at hand, the attracting of a swarm of bees. I will list below, categorised of course, elements which increase your chances of catching a swarm. Ultimately if there are more swarms than containers to house them then you'll will them is nearly anything.
Size
20-40 litres in volume. This is two warré boxes, one national or langstroth brood, 8-12 bars kTBH. Prime swarms will want more space than cast swarms. I have had a cast swarm enter a single warré box (~18 l) that wasn't even nailed together properly.
Placement
I believe 2 metres from the ground is ideal in a location where there is a supply or nectar, water, and propolis. In reality a height you can comfortably reach is MUCH more sensible. It is useful having the bait hive higher eg shed roof, but more so that no one can inadvertently walk into the bees flight path. You will need to have the permission of the land owner and prepare to loose the odd piece of equipment to thieves. I would also suggest it isn't to far from a road. If you think the bait hive it heavy now wait until it's full of unsettled bees!
Entrance
The bees do not care what shape their entrance is. Through experimentation I have found a single entrance with 1 inch diameter works very well. Anything bigger becomes difficult to defend, anything smaller inconvenient. If you wish then you can fit a mesh floor so the bees don't overheat in transport but this must be covered over to attract a swarm in. The darker the better, oddly damp doesn't bother them. The entrance should face south or southest (ish). It is not essential for direction but make sure there isn't a strong wind blowing into the entrance.
Attractant
There are lots of commercially available swarms attractant but they really aren't that necessary. If the box has had bees in before ie coated with propolis etc and smells of bees then this is enough for then. Other things that help are a piece of old brood comb (the darker the better) and a few drops of lemon grass oil (LGO) at the entrance. Use sparingly as too much LGO can put them off. Two drops once every two weeks in more then enough. You can also put some on cotton wool in a zip lock plastic bag left bearly open inside the hive. It is not as good as old brood comb and propolis but as a new beekeeper you won't have that. It that case rub the inside walls of the hive with beeswax too.
Now just wait...... if you can take a look during the day then it is fun to see scout bee interest increasing. If not then a sharp knock in the evening or checking its weight will tell you if you have new tenants. Do not open it until you're sure they have moved in. If you disturb scout bees they're unlikely to return.
If you're lucky enough to see the swarm arrive it is very exciting. Finding bees already there is a close second. It's something like a cross between catching a fish and opening a present. Best of luck!