Where Do Bees Nest In The City?
both sexes can find a wide assortment of urban flowers to meet their
nectar needs. Female bees require pollen for the purpose of provisioning
nests for their brood or young. The full
list of urban plants that attract bees for nectar and/or pollen
is extensive and still growing. But where do females make their
nests in urban settings?
At this time we have limited knowledge about specific
nesting sites of urban bees, especially solitary species. However,
based on wildland bee studies, two general nesting habits can
be expected. The first and most common is ground nesting,
and probably 85% of the bee species use this substrate to build
their nests (see photo at right). Depending on species, females
excavate tunnels into a specific type of soil. At the end of these
tunnels they make a series of brood cells, usually 3-10, lined
with various materials such as mud, leaves, or wood shavings. Each
cell is provisioned with pollen, nectar, and one egg and then permanently
sealed off. The female bee does not continue to feed her brood
as it develops as does the social honey bee. In some bee species
there may be more than one generation of bees per year. In most
there is only a single generation. Spring bees, for example, make
their nests in March or April, and their offspring will develop
slowly over the next 12 months and emerge a year later in March
nesting type is cavity-nesting. That is, some bee species search
for suitable preexisting cavities in old trees or in human structures
of wood or metal, or even mason blocks for making nest cells.
Once located, the same process of nest cell construction and provisioning
occurs as with the ground nesters. Using this knowledge it is
possible to simulate natural cavities with tailor-made wooden cavities
to encourage nesting in home gardens. This can be done with trap-nest
blocks or bee boards (see example in photo), which can be easily
constructed and placed in a yard for convenient viewing of nest
provisioning. Shaded sites are best. Wooden traps can be opened
to more closely observe a nest and its contents (see photo, below-right).
We recommend this kind of intrusion only for teaching classes or
workshops, as once a nest is opened the bees inside will usually
die from exposure.
Another type of cavity-nesting can be observed with
large carpenter bees that chew holes into wood in order to build
their nests. Sometimes they use door and window frames for this
substrate. Although humans regard this habit as undesirable in the
home environment, it reflects a pattern in nature where these bees
would normally be nesting in dead tree branches.