Monday, August 19, 2013

Backyard nest boxes for native bees


I have written several posts about different habitat improvement projects at schools - native pollinator gardens, bluebird nest boxes, etc.  Here is a habitat improvement project from my own yard. This weekend I used some scrap lumber, boards left over from another project, wood from an ash tree I had cut down, some other salvaged wood, and some bamboo to build a nesting box for native bees.  Other than the bamboo, the only things that I purchased for this project was some paint and some hardware to construct the frame.

Bee nesting box placed in the garden

First I built a frame out of some salvaged boards.  I wanted it to look like a small house with a peaked roof.  I had no plans for this so i just made them up as I went along.  Once the frame was done I gave it a coat of green spray paint.

Bee nesting box- made from almost all scrap, leftover, and recycled material


The next step was to fill the frame.  Many native bees next in pre-existing cavities in trees.  Usually these cavities are tunnels that were excavated by beetle larvae.  You can approximate the same thing with a drill.  Because bees come in various sizes, it is important to use different sizes of drill bits.  You may have to purchase long drill bits for this project as the ones included in most bit sets are too short.  Larger bees such as mason and leaf-cutter bees prefer holes that are 4 to 8 inches deep.  Smaller bees, like small carpenter bees, will nest in shorter tunnels.  I used several sizes of drill bits up to 1/4 inch in diameter to drill holes in sections of branches that I had stored for a project just like this.  I also cut sections of bamboo stems to fit in the frame.  When using bamboo, just make sure to leave a joint to plug the back of the stem.

Different-sized holes for different-sized bees

Constructing bee nest boxes does not need to be this involved.  In the past I have made several boxes out of short sections of log with a roof attached.

A simple bee nesting block made from a section of limb

Earlier this year, I buried the end of a 4-foot log upright in our garden and drilled holes in it.  It doesn't get much more simple than that.

A drilled log in the garden provides nesting habitat for lots of bees


So how can you tell is bees are using the nesting box?

The holes that you drilled will start to be plugged - either with mud, leaves, chewed wood, or some combination of all three.  This tells you that a bee has sealed the hole.  Behind that seal, a female bee has constructed several chambers in each of which she has deposited an egg and a pollen packet (food) before sealing off the chamber.  The larva will develop in their chamber and emerge as adults.  At this point of the year (mid-August), the larva will probably not emerge until next Spring.

Sealed chamber right in the middle of the picture

Two tunnels drilled in a knot on a pine log - sealed tunnel near the bottom of the knot.

It's not too late to make a bee nesting block/box for this year.  It is a simple way to help wildlife in your neighborhood.

2 comments:

  1. Amazing!! What size the halls should be? Diameter/depth

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    1. For diameter I use 3/16 up to 3/8 inch drill bits - this equals approximately 4.5mm to 9.5mm. The holes should be drilled to a depth of at least 4 inches (about 10cm) and preferably as deep as 8 inches (20 cm).

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