High Density Housing for Bees

Honey bees are high maintenance for the average homeowner. And for the quarter-acre lot in a tightly-packed neighborhood, inappropriate. Mason and other native solitary bees, however, are a great addition! Mason bees get their name from their habit of building mud walls between the eggs they lay in the tubular chambers they select for the purpose.

The female will pack a load of pollen into the tube, lay an egg, wall it off, and then start the process over again until the tube is full. When she mates, she stores the sperm inside her and only fertilizes the eggs she wishes to be female; unfertilized eggs become males. But she needs a place to do all this!

Back in the days when yards were more unkempt, housing was less of a problem. Nursery practices have allowed homeowners to construct landscapes where the shrubs all stay a reasonable size. Scotts is determined that you have a really green, monoculture yard. The pesticides, the herbicides and above all the lack of weedy growth have conspired to eliminate what used to be common "housing developments" for bees.

So what to do?

Let me say that I love David's quick and dirty bee house over at Montana Wildlife Gardener. One of my favorite features is the back he attaches to the 4"x4" just to simplify the hanging process. It also allows you to drill a deeper hole, since the piece attached to the back will close the back of the hole if you accidentally go all the way through your lumber. My other favorite thing is that his approach is really, really easy to implement with only a saw (just about any variety would do) and a drill with a 3/8" bit. If you've done very little woodworking but would like to give it a try, his design is a great place to start.

Lisa at Dry Ideas took a different approach which has the advantage of tunnels more appropriate to the mason bee. I had concerns about the use of glue, however, because I have no idea what is in the glue I normally use in construction projects and how it might impact the bees. She also uses the 5/16" diameter tunnels that the bees prefer.

The ultimate solution is probably Matt's design for a tray-style mason bee house, which can be easily cleaned each year. Once I've swiped my neighbors router and learned how to use it, I'll get back to you on that. I wanted to give you something you could do pretty simply, so here goes!

I decided to combine these two techniques since my local big box did not have 4"x6" untreated lumber. I bought a single 2"x6"x8' board and stuck it in the back of the Subaru. I used existing scraps for the backs and roofs of the condos. With these instructions you can build at least four condos from a single board (if you have scraps for tops and backs). However, you will need more tools than David used. I used a chop saw (compound miter saw), a drill, a bar clamp, a random-orbit palm sander and a 16 gauge nail gun with galvanized nails and no glue. If you would like to make more than one house, then I would borrow or rent one of these. Otherwise, use finishing nails (pre-drill the holes) or screws that are thin and long. With standard finishing nails, you can probably use fewer than I show here.

As all sources have mentioned, do not use treated or cedar wood for this project. In this image you see the standard pine/fir dimensional lumber available at the big box and two pieces of leftover black locust. (Getting every bit of mileage I can out of this stuff!). The 2x lumber is cut with at a 5 degree angle on one end to establish roof slope. The tall side of each board is 6.5" and the short (front end) of each board is 6 inches. The roof is standard 1"x6" dimensional board, so it is really about 5.5" wide and I cut it to 7" long, with a 5 degree bevel on one end to get a tight fit against the back (matching the slope of the roof established on the 2x lumber. In the photo (left), you can see how the one end of the pine has a slight slope away from the back (which it is laying on top of, in this image). Five degrees is plenty to shed water, and you'll  use less wood in construction than you would if you cut a more aggressive slope.

Once the three pieces of 2"x6" were cut, I wedged them against the front of my assembly table (to get them lined up) and clamped them along their back side. I left the clamp sticking out a little from the back so I could slide the piece intended to be the back inside the clamp. The back piece I cut to 8" long. In this image (right), the clamp is being positioned at the back side of the 3 pieces.

A bar clamp is called a bar clamp because the bottom part of the clamp slides up and down the "bar"-- a pipe clamp, by contrast, uses a pipe as its extension. This particular one requires hand tightening.

Next, I slid the back into position and nailed it to all three pieces. Two nails were used per board at the bottom--nailing about 3/8" up from the bottom. I used 1 1/2" nails, which would mean that about an inch of each ended up in the 2x lumber. Next I did one nail per board across the top, careful to NOT nail directly into the center of each board, since I wanted to drill as far back as possible into each board and I was not interested in drilling through my freshly driven nails.

In this image, the bottom of the condo is on the right hand side of the picture. You can make out the three nails I used at the top of the back in the upper left corner of the image. I know you're thinking that those three nails will never hold... and if this were a toy for your two-year-old, you'd probably be right. For the forces of gravity and bees, however, it should be fine...especially given the next step.

The next step is to attach the top. I removed the clamp from the back and re-attached it to the bottom of the boards, out of the way. Notice that this time I have the bar of the clamp all the way up against the wood. This gets the actual clamping parts as close to the center of the boards as they can get, which will help to make sure the boards are as squished as possible and unable to move during the final nailing and drilling.

I positioned the top so that the 5 degree bevel was placed appropriately against the back, leaving no gap. I then shot 6 more nails--two for each board (at the front and the back) carefully avoiding the center of the 2x lumber chunks.

At this point, it's time to drill! Since each hole is approximately 3/4" from the next one (if you travel vertically down the front of the 2"x6"s), I was able to squeeze 6 holes per board, for a grand total of 18. That's a lot of drilling. A drill press would have made this part a snap, but I stuck with my Makita 18v cordless. I did have to change my battery before I finished all four houses, but then I didn't start with a full charge, either. Here (on the right) is the assembled house, prior to drill work.

This would probably be a good time to discuss why you should bother with housing for bees. After all, if you're going to build the version seen here, you'll spend at least 45 minutes doing it. The fact is that all pollinator species are declining. Blame it on habitat fragmentation, the ubiquitous use of pesticides, the planting of non-native species in homeowner yards--you can pick your favorite, but all of these contributors are bad. Some species of our native bumblebees have declined by 96% in only ten years. The fact that pesticides don't necessarily stay where they are used and have a tendency to build up in the soil means that even if YOU are avoiding the use of them, what your neighbor, your farmer, your city--whatever anybody else is using, it's getting into the water and therefore into plants that our bees depend on for pollen. If you can only do one thing for pollinators (and yourself!), drop the pesticides.

Xerces points out that loss of pollinators impacts biodiversity, as well. When native shrubs don't have enough pollinators to set the fruit, bears, birds and lots of other omnivores don't necessarily get all they need to eat. And the shrub has less fruit set to from which to reproduce. It is a very, very large problem and we likely only have a short, short time to address it. I would encourage you to read the link from the resources below (Xerces Society).

So why a structure for mason bees? The Orchard Mason Bee is a superhero pollinator. Honey bees are only about 3% efficient, in terms of pollinating crops. They are GREAT at collecting pollen. Mason bees, however, are at least

93%

efficient--Henry Ford would have loved them, had he known. It can take up to 750 mason bees to pollinate an acre of fruit. But it takes at least 60 THOUSAND honey bees to pollinate the same acre. In addition, the house you build for a mason bee may end up helping out leaf cutter bees or other native bees that are having trouble finding suitable housing.

Which brings us back to our house. I marked everything in pencil prior to drilling (finding the center of the vertical, mark that, the 3/4" lines down the front, marked those), but if you do this you may find that the drill bit travels a bit and your holes aren't all perfectly aligned. I seriously doubt the bees care. If YOU care, search out a drill press, which will make it much easier to stay lined up on your marks!

After drilling a hole in the back to hang the house with, I finished up by using the sander to knock back the frayed edges at the front of the tunnels. Then used the shop vac to get some of the sawdust out, found that to be only moderately effective and just turned the houses front-side down and banged on them until dust stopped coming out.

The nails held just fine. ;)

Resources:

How to build a tray style mason bee house

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Montana Wildlife Gardener

,

BirdsAmore

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NC State University

,

Dry Ideas

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Pollinator.org

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Xerces Society

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