I have just seen my first male red mason bees (Osmia bicornis) of the year - ten days later than last year. They were checking out the holes in my bee house. This one is just emerging from a hole. You can see his characteristic white moustache.
This one is sniffing out a hole with his antennae.
They have a week or two to build themselves up before the females emerge.
Last year was the first with my bee house. I was pleased that three bees nested in it but disappointed that only 3 of 21 cells (14%) produced bee cocoons because the rest were parasitised. So to boost the local population I bought 30 red mason bee cocoons in the winter .
The cocoons arrived in two cardboard tubes with a hole in one end for the bees to emerge.
Following the instructions I have attached them to the bee house. I don't know what the male/female ratio is or yet know how many will emerge - I hope it will be all of them. There are others from last year around in holes in the wall of the house but I suppose they may have a similarly high parasite rate.
One problem with the bee house last year was that the quadrant filled with hollow plant stems was constantly being pulled about by birds (I suspect magpies, or possibly great tits) looking for spiders. So this year I have put in a wooden block with 25 holes. It is designed to be taken apart at the end of the season so I can salvage the bee cocoons and discard the parasites as I did last year. In that way I hope to continue to build up my population of red mason bees. I'll post another report once the females are out and about.