Bumblebee Domiciles & Nest-boxes

Some bumblebees can be enticed to nest in small domiciles or nest-boxes
placed on the ground, in a hedge bottom or other sheltered place . . . . . .

Construction
Almost any kind of small, wooden box with an entrance hole in one side near the bottom. Size is not critical, anything from 6-12 inches wide, 6-12 inches long and about 6 inches deep, with a detachable roof or lid. The lid should overhang the sides to help keep out rain and can be covered with a rain-proof material to further help keep the interior dry. A few small holes can be drilled in the side of the box, near the top, for ventilation. The entrance hole should be about half to three-quarter inch diameter.

Fig. 1
from Knee & Medler 1965
(The Canadian Entomologist 97, 1149-1155)

Fig. 2
from Cumber 1963
(New Zealand Journal of Science 6, 66-74)

Two types of simple box (single compartment) are shown in Figs. 1 & 2 (above). The box in Fig. 1 has the front and sides extended about 2 inches below the floor (i.e. the entrance hole is in fact more less level with the floor inside). The open space below the floor reduces dampness creeping in from the ground. The box in Fig. 2 has the floor constructed from a thick piece of timber (about 2 inches thick) which is extended forward as a landing platform. The thickness of the timber again helps keep the nest compartment dry.

Some people have tried more elaborate boxes with two compartments, as shown in Fig. 3 (below). This design is useful if the colony has to be moved, since a temporary supply of food (pollen and sugar-water) can be placed in the ‘vestibule’ part of the box until the move is accomplished. Also, to enable viewing of the colony without disturbing the bees, you can install sliding glass covers below the main roof or lid of the box, as shown in the diagram of Fig. 3, although this may cause problems with condensation.

Fig. 3
(a) Two-compartment nest-box with lid removed;
(b) Diagram of similar nest-box with lid removed to show sliding glass covers (see text)
from Cumber 1963 (New Zealand Journal of Science 6, 66-74)

There are numerous reports of bumblebees nesting in bird-boxes. Those in Fig. 4 (below) are made from hollowed-out silver birch trunks, but almost any kind of bird-box could be used.

Fig. 4
from Nielsen 1938
(Videnskabelige Meddelelser fra Dansk naturhhistorik Forening Kjobenhavn 102, 1-6)

Nesting material
It is a good idea to line the floor area of bumblebee domiciles with corrugated cardboard. This helps absorb excess moisture and aids future cleaning. Whatever kind of domicile is used, the nest compartment must be provided with nesting material - bumblebees frequently use abandoned mouse nests, and if such material is available it is ideal for lining the nest chamber of the domicile. However, you can substitute different kinds of nesting material, such as upholsterers cotton, mattress stuffing, hair felt, insulation fibre (but not fibre-glass), or shredded grass, straw and dry moss. Cotton-wool should be avoided since it gets tangled on the legs and bodies of bees. Shredded grass and moss from an old birds nest is OK, but it must be dry.

Placement
On the ground along fence rows, hedges, windbreak strips, borders of woodland, in stump piles, or other locations where queen bumblebees may have been seen searching for a nest-site in spring. Choose warm, dry, sheltered places, preferably south-facing but shaded from direct sun. Place a large rock or concrete slab (weighing about 10lb) on top of each box to prevent the lid dislodging and disturbance by potential predators (see Fig. 1).

The success of natural colonisation of domiciles by bumblebees is very unpredictable and at best is unlikely to exceed 25% (1 in 4) - hence a fairly large number of boxes have to be used.