>>In the wild, they don't like drafts but have a top vent of some sort even if it's just dry rotten wood overhead in a tree.
>Can you give your source for this ?
>Any upper entrances in trees I have ever seen are always propolised shut.

I am relaying personal observations.  Most tree colonies I've worked with had a single entry hole.  Inside the hollow above the colony, there is typically a dead wood core of the tree.  In my opinion, this dry wood (without direct opening to the outside) acts like a sponge for the moisture generated by the wintering cluster.

I came across only one tree colony that was only 3 feet up from the ground.  There was a main entrance hole the size of a man's fist.  The tree was decaying from the inside and, during bee vaccing, I noticed some bees using a couple of holes perhaps 3/8" in diameter when my body was in the way of the main entrance.  Those extra holes were not propolised but the were located 6-10" above the top of the combs that were attached to the dry wood canopy.

Back in my early days, when I followed advice to drill 1" vent holes under the hive body handles, the bees would certainly propolise these as long as they were close to the nest.

These days I use full footprint screen on top of the hives for ventillation.  The best summer method in my opinion.  The bees will often propolise large swatch of the screens starting from the corners and seal a lot of the center area with wax in the late summer when nights become cooler.  There will be some area unsealed though.

I meant to ask - do you get many/any feral colonies in trees or structure in the UK?

Waldemar

******************************************************
* Full guidelines for BEE-L posting are at:          *
* http://www.honeybeeworld.com/bee-l/guidelines.htm  *
******************************************************