Carpenter bees work the mulberry trees

The air hums with a deeper note than usual near the white mulberry trees in Durham's neighborhoods. If you step outside now, the sound carries a purposeful weight, different from the higher pitch of smaller bees. These are eastern carpenter bees, and they move through the canopy with deliberate focus.

Each female carpenter bee measures nearly an inch long, her black body gleaming with a metallic sheen. She hovers at the clusters of white mulberry flowers, her wings beating fast enough to blur but slow enough to produce that distinctive low drone. The white mulberry is an invasive tree from Asia, but the carpenter bee treats it like any other nectar source. She extends her long tongue into each tiny flower, collecting nectar while pollen grains stick to the dense hairs on her legs and abdomen. When she moves to the next flower cluster, some of that pollen transfers, completing the tree's reproduction whether she intends it or not.

The timing works perfectly. White mulberries bloom in late spring and early summer, just as the carpenter bees emerge from their winter dormancy and begin their own reproductive cycle. The female bee needs protein-rich pollen to provision her nest, which she excavates by boring perfectly round holes into dead wood or the eaves of buildings. She chews through the wood fiber with her powerful mandibles, creating tunnels where she will lay her eggs and stock each cell with a ball of pollen mixed with nectar. The mulberry pollen provides essential amino acids her larvae need to develop. In return, her visits between flowers ensure the tree produces the dark purple fruits now ripening on the branches.

This relationship extends beyond the mulberry trees. Carpenter bees visit native black cherry and serviceberry as well, both of which also fruit in midsummer. They work the same pattern: hovering at flower clusters, probing for nectar, picking up pollen, moving to the next tree. Their size allows them to handle larger flowers that smaller bees cannot access effectively. Their long tongues reach nectar that remains out of reach for other pollinators. They are not the most efficient pollinators for any single plant species, but they are reliable generalists, working whatever blooms the season provides.

The low hum continues overhead as another carpenter bee approaches the mulberry canopy. The sound carries a quality of concentration, each wingbeat measured and deliberate. If you look up now, you might catch the metallic glint of her body as she moves between the pale flower clusters, her movements unhurried but purposeful in the warm summer air.