Initially I’m focused on Bumblebees.
Section 3 of the publication “Conserving Bumblebees” has three pages discussing bumblebee habitat. Most of the work on discovering bumblebee habitat comes from Great Britain. Because the population density is great throughout the country most nests were found near where people lived ( Because that is where they were able to look most often)
In a nutshell, bumble bees nests are usually found near or below ground level. Because of this, their nests are in areas that are not disturbed. Disturbed areas would be those walked upon, mowed, grazed-on or tilled. In developed areas this is likely to mean in green corridors under power lines and along small streams and drainage areas where native vegetation grows even in our cities.
There is not a lot to go on here. I’ve copied these next portions directly from the text and used italics to indicate this.
“ suggesting that bumble bees are opportunistic in nest site selection. Some species do have nesting preferences, but will take advantage of many different locations and materials.
The most comprehensive study analyzed over one thousand nesting sites. Of the top five nest locations—bird box, cavity in rock wall, compost pile, under building/man made structure, hole in the ground, four were artificial structures and they represented more than three quarters of observed nests.
While there may be some surveyor bias here as citizens are more likely to be looking where people live, it still means that gardens and natural areas with buildings, rock walls, bird boxes, etc. can provide significant habitat. This adds to the growing evidence that urban areas, parks, gardens, and managed natural areas can be significant refuges for bumble bees
Later sections of the text added
Most bumble bees nest underground, often in abandoned holes made by ground squirrels,and
Some species do nest on the surface of the ground (in grass tussocks) or in empty cavities (hollow logs, dead trees, under rocks, etc.). To which I would add that considering what we have to work with here in New England, this should be bumblebee nirvana.
In gardens, nests are often found in compost piles or unused bird houses. This would be an argument for keeping a compost pile rather than a rotating compost drum
Overwintering: Only the already impregnated Queen bumblebee overwinters to start again in the spring.
Queens most likely overwinter in small cavities just below or on the ground surface.
They have also been noted overwintering in man-made habitat such as woodpiles, rock walls, and in sheds.
For most of us, the advice is the same as for other bees. Leave some area “rough” and in its natural state. But we can create opportunities to add cracks and crevices in garden walls, particularly where foot traffic is low.
In the above picture, a raised bed garden was created to hide a tree stump. The current fashion when a tree is cut down on your lawn is to bring in a large machine to dig out the tree roots so that the surface can be smoothed over and grass planted. In this picture, a tree stump was cut off close to the ground and left in place, but buried with approximately 1 foot of garden soil. This was then surrounded by bricks to level out changes in the grade and topped with slightly more decorative blocks that provide for sitting. The otherwise unsightly tree stump became a raised bed flower garden. The spaces between the bricks might provide nesting or over-wintering space.
Late 2016 update: During the early summer of 2016, I followed dozens of solitary bumblebees as best I could keep up with them, hoping to discover where a bumblebee nest might get created. The area that received the most inspections by bumblebees was along a garden fence where I had placed shipping pallets along the fence. I had cut shipping pallets in half and placed them on the ground outside of the garden fence. These half pallets held decaying leaves in place creating about a 2 foot wide weed-free zone of “edging” along the garden fence. Several seasons accumulation of decaying leaves on top of the pallets created many cavities and hollows under the individual boards. It was a nesting place for crickets and field mice and voles, as well a cafeteria and temporary shelter for garter snakes and chipmunks and squirrels.
I suspect the cafeteria aspect kept the bumblebees from nesting there or soon discouraged those that might have tried to nest there. The one thing I did discover about these mice nesting sites is that they can harbor rich breeding grounds for ticks, the suspected source of Lyme disease. Ticks are an ongoing and growing problem in this area. Because of this, I will remove the pallet perimeter while the weather is still quite cold, but leave the decaying leaves in place. A mouse-eating house cat or barn cat is the only organic tick defense I can think of that won’t bother bumble bees.
During all of 2016, I failed to discover a single bumblebee nest, active or abandoned.
During early October before our first killing frost, my ever-bearing raspberry flowers attracted a great many bumblebees, even when too cool for honeybees to be out foraging. From this, I took comfort in knowing that bumblebees were likely to overwinter nearby. However, their nests or over-wintering spot was not likely near the raspberries and I soon lost sight of them as they completed their raspberry foraging and flew off in inconsistent directions.
This bumblebee nest location hunt will continue in 2017.