Commercial bumblebee nest boxes are expensive and have a low success rate leading to great disappointment. However, take heart, even professional scientists have a low success rate when it comes to bumblebee nest box occupancy – sometimes fewer than 10% of boxes will be occupied. So what can be done increase your success? Well there are a few basic things to check first.
Get the right size nest box for the bumblebees in your garden. If you have Bombus terrestris, lucorum, pascuorum or lapidarius you will need a box around the size of a tissue box or even a small shoe box. The other species of bumblebee have much smaller nests – anything from a coffee tin to a tennis ball size will do them. So the first thing to do is check the species of bumblebee using your garden. To find out which species of société nid de frelon bumblebee you have see the resource link below for an easy guide to the most common species. And even if you cannot identify every species in your garden, you can play it safe and provide 2 sizes of nest box.
Place the nest box in the right place for the right species. All species like to be sheltered from the north wind, but a full south position in sun can also be too hot for the above ground nesters.
- Larger boxes. Most commercially sold nest boxes are made for the species that have larger nests, but you see photographs of them placed above ground. This is very misleading as most of these bumblebees actually prefer to nest either underground or on the ground. So if you have a large type nest box you will have to either bury it or place it on the ground. Now this is not much help if it is one of the more expensive boxes with a top allowing you to observe the bumblebees nest. However all is not lost. There are ways of fooling bumblebees into thinking they are nesting underground when they are not. It is quite simple – you attach a hose to the entrance, and as long as the hose is dark, and the box is well placed the queen will think she is entering a tunnel. And as these species favourite nesting place is an abandoned rodent nest at the end of a tunnel, you are providing an ideal nest site. If you do not have an observation nest, then the next best place for a nest box is under the garden shed, either on the surface or partly buried, and it would still be a good idea to attach a piece of hose to the entrance to fool the queen into thinking she is entering a tunnel. You can also place it buried or partly buried under a slate or paving slab, under decking, or steps. Wherever you place it it should be protected from rain..
- Smaller boxes. Bumblebees with smaller nest sizes tend to be the above-ground nesters. For these it is much easier to find a good nest site in a garden. In fact you may already have one without knowing it – a bird box! Usually the box hasn’t been cleaned out from the previous year, and the nest material left behind by the birds is perfect for bumblebees. Another very good site is a dry stone wall. You can replace one the of the stones with the bumblebee box, a coffee can with a hole cut out of the plastic pop-off lid, or even a tennis ball. I pushed a tennis ball with a hole cut out low down in an old wall hoping for bumblebees, but got a wren instead, however I will not clean out the nest as I might get a bumblebee queen nesting there next year. As with the larger boxes do make sure you protect the entrance from rain.
Nest material. Commercially sold boxes usually come with nest material, and it is usually fine, and even if the box has not been occupied, if the nest material is still dry it is quite alright to leave it for another year. For the underground nesters the very best nest material you can get is simply the dry contents of a mouse or vole nest complete with droppings! Now I realise that this is not always something easy to find or desirable to use, so you can use chopped up dry grass clippings, dried moss, an old bird nest, even old horsehair stuffing from an old chair or sofa. The main thing to remember is that it must be dry. Never use cotton wool or any synthetic material as the bees will just get tangled up in it. If the nest box is big enough it is a good idea to place a cushion of scrunched up chicken wire on the base and place the nesting material on top of this, as this will keep it dry and allow debris to fall to the bottom to keep the nest clean.