Given the large amount of concrete and other impervious surfaces in New York City and surrounding suburbs, it’s interesting that 65 percent of the area’s bee species nest in the soil. Common soil nesters include miner bees (genus Andrena), small sweat bees (genus Lasioglossum), long-horned bees (genus Melissodes), and plasterer bees (genus Colletes). Including the nest parasites that depend on soil-nesting bees as their hosts, roughly 70 percent of bees in the city depend on soil for nesting. Sandy soil in coastal areas, silty banks near streams or rivers, sunny open fields, and the edges of hedgerows and forests are ideal, but even sparsely vegetated areas in parks or backyards that are not trampled or disturbed can serve as good nesting sites.
The quality and location of the soil matters. Studies have indicated that many bees prefer well-drained, sandy soils that are loose and friable so they can easily burrow. They also favor south-facing slopes. However, while this may be generally true, the specific soil texture and location required vary by species. For instance, two species of mining bees in the genus Anthophora build burrows in hard clay banks. Some bees can be observed nesting in garden soil, and some have even been observed building nests in potted plants. One observer found a plasterer bee building a nest in a potted Venus Fly Trap plant that had been placed outside for part of the summer!
When looking for bee nests in the soil, be aware that many animals build nests in the soil. If you see a hole it could be a bee, but it also could be a beetle, worm, wasp, ants, or something else. One way to find out is to place a plastic cup on the top of a suspected soil bee nest and wait to see what emerges. Our experience is that a garden, park, or other site that at first glance seems devoid of soil-nesting bees may, upon closer inspection, actually have many nests.
After soil, the next most common nesting location for bees in New York City is cavities, accounting for 24 percent of the City’s bees. Cavity-nesters are also often called “aerial nesters” because the cavities are typically in plant stems above the ground. Common cavity-nesters include leaf-cutter bees (genus Megachile), masked bees (genus Hylaeus), and mason bees (genus Osmia). Shrubs in which cavity-nesters are often observed include roses, hydrangeas, and lilacs. In general, however, any plant with pithy or hollow stems may be suitable for cavity-nesting bees. For strategies on protecting and providing bee nesting sites, see Management.
Just 6 percent of New York City bees nest in hives. This group includes the European honey bee and bumble bees. European honey bees may nest in managed hives—honey bee keeping recently was legalized in the City—or exist as feral colonies in hives located in parks, cemeteries, and other locations. Feral colonies are created when a new or deposed queen leads a swarm to a new nest location outside of the managed hive. This can be in a tree cavity, a hole in the side of a house, or a variety of other locations to which honey bee keepers are often called to remove bees each spring.
Bumble bees often nest in abandoned rodent nests, and possibly in tree cavities. Bumble bees are very abundant in New York City, so it is curious that nests are rarely reported. One nest was identified by citizen science bee watchers in ground ivy at Madison Square Park in Manhattan. By careful observation of bumble bee flight patterns, it should be possible to locate other nests.
Very few bee species in New York City are dependent on hard or rotting wood for nest sites. Three species of small sweat bee (genus Lasioglossum) and one species of green metallic bee (Augochlora pura) nest in rotting wood. Just one species, the large Eastern Carpenter Bee (Xylocopa virginica), constructs nests in hard wood. The entrances to carpenter bee nests can be identified as nearly perfect dime-sized circles, which often have a small pile of sawdust on the ground below them. By placing your ear to the wood near a nest hole, it is often possible to hear the female bee chewing wood as she excavates the nest tunnel.
These nesting sites need to be close to good food supplies—fields or forest edges or gardens with abundant yet diverse nectar and pollen sources that are available throughout the season, from early April through October. Also essential are so-called habitat corridors that connect nesting and foraging sites, to allow bees safe passage as they travel to and fro gathering pollen and nectar for their young. For more information on nesting requirements, see Management.