Sorry, no data to backup my thoughts today… but I feel that the number of bumblebees I saw in the last two years doubles the previous 30 years of my life. Uppsala is a smallish city in Sweden. Has lots of flowers (along all the season), cool summers (from my spanish perspective I may even say cold) and patches of semi-natural grasslands and forests mixed within the city. And lots of bumblenees. Mostly B. terrestris, and B. lapidarius, but I also see frequently B. pascuorum and B. hypnorum, and is not rare to see B. hortorum*.
I don’t make an effort to look for them, but I saw them waiting for the train to pass (yes, railroads have a lot of flowers) or when I am playing with the kids. Walking in spring in the forest patches within the city implies watching your feet to avoid steeping into queens. I even spotted two different bumblebee nests (B. terrestris and B. lapidarius) using man-made structures in playgrounds. Common! I’ve not seen any another natural bumblebee nest in the rest of my life, despite looking for them in several occasions.
I was talking yesterday with a colleague that is surveying bumblebee in grasslands and forests around the city and he is frustrated because he sees very few bumblebees**. So it’s not only Sweden which has lots of bumblebees, but particularly small “green” cities. Maybe cities are really good habitat after all, at least for a few species (See also NYC bees). The same pattern can be seen in bird species, where a few species thrive in cities, so probably I am not saying anything new.
*Id’s on the fly
**4 individuals /8 hours in an area with some flowers in a nice sunny day! that’s the worst day, usually he gets ~20 though