This year I tried four types of houses and I wanted to share my harvest report and feedback about different designs. I'm curious what you've observed as well and would welcome comparisons and new ideas for next spring.

CONDITIONS
2010 was a very bad year for mason bees in the western US and Canada - record-breaking cold very late into the season. In Seattle, where I live, the weather was cold and stormy, and the bees didn't emerge until after most of the fruit trees were finished flowering. Still, my population increased.

SITE
House in the City of Seattle, in the pacific northwestern USA. The climate here is cool and maritime, the local landscape for the bees is small city yards and street trees.

PLACEMENT
All of these houses are mounted on the south side of the house, the sunniest location I have. They got sun from about 10am to 4pm, but on the south side, they were exposed to more wind and rain as well.

EMERGENCE
I started with cleaned loose cocoons - roughly 150 females and 200 males. The loose cocoons were placed in emergence drawers/trays/boxes. I released them in several "waves," but regardless most of them emerged in the same one-week period in April, after three straight days of temperatures above 70 degrees. Nest systems that had emergence boxes were immediately occupied. The one house I had that didn't have space for emergence was occupied last and only at the end of the season.

NEST SYSTEMS

#1 - Commercial system - BeeDiverse
Wood shelter with interlocking plastic trays. Bare plastic only, no liners.

#2 - Commercial system - Pollinator Paradise
Metal shelter with interlocking wood trays secured by bolts. Half lined with white pre-slit straws; half left bare.

#3 - Individual manufacturer - Pasquale G
Wood shelter, loose solid wood trays with drilled round holes. Holes lined with rolled brown paper + rubber stopper at back.

#4 - Individual manufacturer - Hutchings Bee Service
Wood shelter, individual solid wood trays with square channels OR open tray space. Each tray covered by clear plastic for viewing; very deep 12" tubes.

DATA

#1 BeeDiverse
Harvest
Filled tubes: 29 out of 30
Females:46
Males: 60
Mortality
Pollen mites: 12
Mold or chalkbrood: 4
Misc predators: 13
Total mortaility: 27.4%

#2 Pollinator Paradise
Harvest
Filled tubes: 64 out of 98
Females: 191
Males: 241
Mortality
Pollen mites: 50
Mold or chalkbrood: 0
Misc predators: 29
Total mortaility: 18.3%

#3 Pasquale G
Harvest
Filled tubes: 35 of 35
Females: 90
Males: 124
Mortality
Pollen mites: 15
Mold or chalkbrood: 0
Misc predators: 8
Total mortaility: 10.7%

#4 Hutchings Bee Service
Harvest
Filled tubes: 1 only
Females: 7
Males: 4
Mortality
Pollen mites: 5
Mold or chalkbrood: 0
Misc predators: 8
Total mortaility: 45.5%

DISPERSAL
I started with about 150 females, but only 50 stayed to next - a dispersal rate of 67%.

OVERALL REPRODUCTION
(after end-of-season cleaning)
On average, each nesting female filled 2.5 tubes and produced 15 cocoons. I started with 350 cocoons and ended up with 763 cocoons.

SYSTEM FEEDBACK

#1 BeeDiverse
This system is readily adopted by the bees and easy to clean and manage. It also consistently has the highest mortaility rates, year over year, and is the only system I ever see mold in. Its peaked roof allows for a variety of emergence containers - very handy.

#2 - Pollinator Paradise
I used a 50/50 mix of slit paper straws and bare wood tubes. The bees preferred the bare wood by almost 50% more. This system produced a high number of cocoons per tube. Mites were able to migrate between tubes due to the "interlocking tray" design, but I don't think it significantly impacted mortality. It is a pain in the neck to clean because all of the trays are adhered to a single backing. The slit paper straws were easy to open, and if all of the cocoons looked healthy I simply left the tube intact.

#3 - Pasquale G
The bees favorite design -- immediately occupied and actively used - several design features seemed to appeal more to the bees here than in other houses - slighly wider tubes, a perch for landing/sunning, and the tube liners that stuck out a bit from the wood trays--these appeared to be easier to seal with mud, and these had more solid, smooth mud caps than the other houses. Brown paper was more popular than white. Lowest mortaility of all systems. Easy to clean and good solid wood protection.

#4 - Hutchings Bee Service
HBS systems have a very unique design - individual loose trays are covered by thin plastic sheets, which allows you to gently pull out the trays and observe nesting progress - lots of fun for a hobby. I question if the plastic promoted higher humidity (and more pollen mites) but the weather made it difficult to judge. The 12" deep tubes produced a high number of females per tube. The condo was not immediately used by the bees - perhaps because it was the only system that didn't allow space for an emergence box. Next year I will "seed" it with some filled tubes and see if it is adopted sooner.

That's it. All followup reports, feedback, comments and suggestions welcome.

On a side note, here is whre I bought my bee house and bees.

Dado House

Yes, I think they need a closed hole to work with and also it cuts down on parasite access.

You might want to try bolting the plates together with either bolts or some pieces of all thread rod and nuts or some sort of clamp arrangement. Or maybe try plywood or wood that has been 1/4 sawn for a vertical grain?

I lam going to try out that idea of making a nest with boards and dados. Should be a lot faster than drilling.
Might also see about making a board with 1/2 round grooves top and bottom so i can still use disposable tubes for handling and sanitation reasons. I have had good success with blocks of bored timber and using parchment paper linings. However, your idea would be so quick to make that you could just make a new one every year rather than cleaning a sterilizing the used one.

Still, if it works is still the best litmus test.

That, and either try bolting the boards together as mentioned by gyozu, or straps, which we use on our wood laminates. (see products in http://www.crownbees.com)

the major problem you will have is that the pollen mites can easily transfer across the grooves if the boards aren't made well. :(

Question 2.... I live in a cold climate and was wondering about placement. Some state eastern placement for sun, others mention southern. Almost all of my storms come in from the south. Which could be snow, rain, hail, wind etc...

Thanks

1) Height or width of the overall house isn't very important for the average residential gardener. What -is- important is tube diameter and the presence of orienting marks for the bees, like colored straw tips, or patches of color, or a few straws sticking out further than the rest. These bees like irregular surfaces with lots of identifying marks. They can see blue, yellow, green, and black.

2) Ideal placement is where 1) it will get sun in the morning to help the bees warm up for flight and 2) It's protected from weather.

I live in Seattle and place my bees on the south side of the house because they get the most sun there (7 hours during the warmer part of the day) Our storms in Seattle come in from the south, so that also means the houses are exposed to a lot of rain and wind, which 1) encourages them to disperse (fly away and not return to nest there.) and 2)creates great moist conditions for pollen mites. That was a bad idea last spring, which was cold and wet and windy.

This year I'm placing some houses on the south side of the house and some on the east side to see which perform best. The east side gets five hours of sunlight during a colder part of the day.

For the ones on the south side, if we're in for stormy weather, I have two options: 1) build a more protective roof over each house or 2) Take the entire house (bees and all) and put it in a bag in the fridge for about 24 hours. SARE's guide to Alternative Pollinators says you can do this for up to five days with no harm to the bees. We'll see how that idea works out. :-)