Tuesday, March 15, 2016

More Woodworking for Bees - A Bumblebee Nesting Box

I am an old hand at creating homes for native bees.  It is easy to make a nesting block that mason bees, leafcutter bees, and small carpenter bees will love.  Other bees are satisfied if you leave a bare patch of soil or hollow stems for them to nest in.  However, there is one group of native bees for whom I have never tried to create a nesting site - bumble bees.

Not any more.

My new bumblebee nesting box - waiting to be placed in its new home


On Sunday (13 MAR 2016), I built my first bumble bee nesting box.  Bumblebees have different nesting requirements than other native bees.  Like the European Honey Bee, most  bumblebee species form colonies with a queen and workers.  Unlike the honey bee, these colonies only last for a single year.

Each fall new queens are born.  They mate and then seek a place to hibernate.  In the spring those that survived winter emerge from hibernation and begin seeking a place to establish a colony.  She often searches out an abandoned rodent burrow or some other underground cavity.  Sometimes she will nest in a cavity in a tree or even simply at the base of a clump of grass.  Once she establishes her nest, she will continue to forage for nectar and pollen until she has enough sterile daughters (workers) to take over foraging.  Late in the summer she will lay eggs that will become fertile queens and drones (males).  After the young queens and drone have left the nest as adults, the colony's work is done and the remaining bees will eventually be killed by cold temperatures.

Many species of bumble bees have recently undergone severe population declines, with one or more species having actually gone extinct.  Part of the reason for this decline may be related to habitat loss as many former nesting sites in fencerows and field margins have been converted to crop production.

My gardens at home always seem to have a healthy population of bumblebees.  I am hoping that by adding a nesting box to the garden I will be able to attract a queen and be able to observe the growth of a colony.

The nesting box that I constructed is made from cedar lumber, left over from other projects.  The sides of the box are made from 1x8 lumber and the bottom and lid are pieces of 1x10 lumber.  The edges of the lid were ripped down to 2 inches from a piece of 1x10.  Overall the dimensions of the box are approximately 15 inches long x 9.25 inches wide x 9 inches tall.  The lid measures 16.75 inches long x 11 inches wide x 2 inches tall.  I used both wood screws and construction adhesive to assemble the box.

Front dimensions of nesting box

Lid dimensions

Outside length and width of the nesting box


The interior of the box is divided into two chambers by a scrap of 2x6.  A piece of 3/4 inch (inside diameter) PVC pipe provides access to the first chamber from the outside.  A 3/4 inch hole drilled into the 2x6 divider provides access to the second chamber.  Ideally, bees will nest in the inner (second) chamber.  This chamber should be lined with some sort of soft nesting material for the bees to begin nesting on (wood chips, cotton, straw, etc.).  I added some paper rodent bedding and will probably add some grass clippings as I do spring cleaning on the garden.  This second chamber also has several ventilation holes drilled near the top.

Inside dimensions of the nesting box

I plan on placing this box on the ground in a corner of the garden formed by an angle of the house.  This site is under the eaves so it is somewhat protected from rain.  The location is also shaded for much of the day with full sun only in the early morning - this is important so the box (and its occupants) do not overheat.

I am going to wait a coupe of weeks before I place this in the garden - there are not really any flowers as of yet.  In the meantime, I plan on taking it in to the office and displaying it with the hope that it will inspire others to think about native bees.

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