Nature Watch: Flight of the Bumblebee

About the author: Steve Ellis is a naturalist and Land Trust member who enjoys sharing his love of the natural world. His blog series, “Nature Watch,” will appear each month in “Habitchat,” chronicling native plants and wildlife you can expect to see during that particular time of year. We thank Steve for sharing his passion, illustrating the importance of island conservation.

Overview

March weather is usually much too cold for most pollinators, yet several native plant species bloom this month. They rely on the flight of the bumblebee.

Bumblebees are particularly well adapted to fly in temperatures that keep other bees grounded. The non-native honeybee, for instance, is unable to fly until the air temperature rises to 59° F. In contrast, one bumblebee was seen flying at a chilly 26°.

Many advantages help bumblebees get an early spring start. Hair covers their entire body and insulates them from the cold. Bumblebees’ large bodies also retain heat better than slimmer bees. The main factor in their favor is their ability to uncouple their flight muscles – found in the thorax (the second segment of a bee) – from their wings. The muscles are then employed at a furious rate, generating  heat through shivering. A 40° rise in temperature is common through this process.

Fertile queens of some species will emerge in March. They can be seen flying low over the ground as they search for sites useful for starting new colonies. It may take up to two weeks to find the right hole. Typical sites are under decaying stumps, beneath an exposed tree root, or an unoccupied vole burrow.

Once a site is selected, the queen begins gathering pollen and places it in a clump on the nest floor. Egg-laying ensues. The hatched young bees feed on nectar-moistened pollen as they grow to adulthood.

Local entomologist Joseph Sheldon has identified seven bumblebee species still living on our islands.  Each has a habitat preference and time of queen emergence. The most common are yellow-headed (late April emergence), fuzzy-horned (March), yellow-faced (March) and black-tailed (April).

You can help bumblebees by leaving patches of undisturbed vegetation on your property. Commercial bumblebee boxes are available if no vole holes exist nearby. Limiting pesticides and planting native flowers and shrubs that bloom at different times will help ensure future generations of bumblebees.

Yellow-faced Bumblebee by Martha Ellis.

Fauna: Yellow-faced Bumblebee (Bombus vosnesenskii)

One of the most common local bumblebee species is the yellow-faced.

Identifying bees is very difficult and usually requires a hand lens and a key delineating the differences between the species.

Yellow-faced bumblebee queens are large – nearly one inch in length. They have short, even hair covering the entire body. The face and front part of the thorax is yellow, while the rest of the body is black, except for one yellow band around the abdomen (the segment behind the thorax). The large area of black on the body is a definitive field mark.

Described as fat and slow, yellow-faced bumblebee queens emerge in March to begin the new colonies.  Their eggs hatch and mature into workers in late May or early June; drones and queens follow later in summer.  Total bees in the colony will eventually reach 200 to 300. By October, only the new fertile queens are still alive.  They’ll find hibernation places to wait for the coming spring.

Yellow-faced bumblebees are found in many habitats, including grassy areas, open woods, thickets, and orchards. Their long flight period and wide distribution make them one of our islands’ most important pollinators.

Tall Oregon Grape by Martha Ellis.

Flora: Tall Oregon Grape (Berberis aquifolium)

Tall Oregon grape – not related to true grapes – is an early-bloomer that relies heavily on bumblebees for pollination.

This shrub grows from one to seven feet tall. Leaves are evergreen, one to three inches long, and holly-like, with sharp tips. They’re shiny green above and paler below. Flowers grow in clusters of bowl-shaped bright yellow blossoms. Following pollination they develop into purplish-blue berries with a waxy coating.

Many bird species eat the berries. This handy shrub also plays an important by providing cover for birds, small mammals and amphibians. Predators are reluctant to enter a thicket of Oregon grape’s sharply-pointed leaves.

Look for tall Oregon grape in open forests, field edges, and along roadways. Those growing in full sun tend to bloom in March, while those in partial shade bloom later in the season.

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