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Woodlots - a Refuge for Ontario’s Native Bees

This spring I had the pleasure of visiting Kelly’s Blueberry Farm near Bancroft. The blueberries were in bloom, and the bushes were alive with hundreds of bumble bees and other native solitary bees. Notably, the blueberry growing area on the Kelly’s farm is surrounded by forest on all sides. Few insecticides, if any, are used and all manner of wild flowering plants are allowed to flourish on hillsides and natural lands. On a tour of the woods I saw numerous native flowering plants on the forest floor and the forest edges boasted staghorn sumac, virgin’s bower, wild apples, choke cherries, pussy willows, meadow sweet, and many more flowering shrubs, all of which are nectar and pollen sources for bees. The trees themselves, although mostly wind pollinated, are visited by bees in early spring when other pollen sources are scarce and tree pollen is plentiful. My guess is that many of Ontario’s wooded areas are much the same--expanses of good foraging habitat for Ontario’s bees.

RPBB bombusaffinisThe Rusty-patched Bumble Bee (Bombus affinis), classified in 2010 as endangered, and has not been seen in Ontario since 2009.The Rusty-patched Bumble Bee (Bombus affinis), classified in 2010 as endangered, and has not been seen in Ontario since 2009.Ontario has more than 400 species of native bees. A handful of those bees are bumble bees that live in small colonies. Bumble bees are large, fuzzy bees that come in an array of yellows, blacks, white, orange and brown; the arrangement of those colours differs by species and is one of the key ways in which the species are identified. The Common Eastern Bumble Bee and the Tri-coloured Bumble Bee are common in Ontario and can be easily recognized by the novice bee watcher. Another bumble bee, the Rusty-patched Bumble Bee, a black and yellow bee with a small rusty patch on its abdomen, was common in Ontario thirty years ago, but in 2010 was classified as endangered the Ontario Species at Risk list. The Rusty-patched Bumble Bee has not been found in Ontario since 2009 although a concerted effort by experts and bee spotters has been made.

Although bumble bees are more noticeable, most of Ontario’s bees are solitary bees that do not form colonies at all. These solitary bees do not have queens - each female makes her own nest, and once mated, she forages for pollen and nectar to provision food for her offspring. Most have only one adult generation per year and most spend most of their lives in immature stages in the nest, active as adults only a few weeks of every year. Solitary bees come in all sizes: Carpenter bees are almost the size of bumble bees, whereas Perdita species are about the size of a grain of rice, with every size in between. Coloring is equally varied - dull browns and greys prevail but some are metallic blues and greens (blue orchard bees (Osmia sp.) and green sweat bees (Agapostemon sp.) for example), others are yellow and black (the cuckoo bees of the genus Triepeolus for example), and still others sport white masks on their faces (Hylaeus sp.). Learning to identify these bees is more of a challenge than learning to identify bumble bees because they are smaller in size and move quickly while foraging. However, once you take the time to observe, noticing them in the woodlot and at the woodlot edge will become second nature.

carpenterbee xylocopavirginicaCarpenter bees (Xylocopa virginica) are almost the size of bumble bees.Besides foraging habitat, native bees need nesting habitat. Bumble bees can nest in the ground, often in abandoned rodents’ nests or above ground in tussocks of grass. This sort of nesting habitat can often be found at the naturalized edges of wooded areas or in the rock piles left when settlers cleared fields. Solitary bees nest in a variety of materials. Most nest in the ground by making small straw-sized tunnels with short side shafts in which they build cells and lay eggs. Other native solitary bees nest in cavities excavated in pithy or hollow stems of plants. Forest edge plants such a sumac, elderberry, black berry, thimble berry, and raspberry all provide nesting habitat for these bees. Some bees such as leafcutter bees will nest in rotting logs or deadwood, an amenity that most woodlots can provide.

The simplest approach to providing nesting habitat for native bees in the woodlot and surrounding areas is to protect the nesting areas that exist naturally in those landscapes as follows:

  • Tolerate dying trees and standing deadwood if it is safe or practical to do so. Many bees use holes bored by beetles in wood for nesting.
  • Protect sparsely vegetated slopes, and leave areas of bare soil, especially if you see small holes about the size of a straw in those areas. Those holes are the entrances to ground-nesting bee nests. Ant nest entrances are much smaller and look different.
  • Avoid disturbance in grassy thickets and areas of dense cover. Some bumble bees nest in this kind of habitat and often the flowering plants that bees forage on are found here too.

Native bees are increasingly being recognized as major players in the pollination of many crops. They certainly are critical for pollination of native plants, which in turn provide food for many birds and mammals. For this reason, bees are considered “keystone” species. Many woodlots, by their nature as natural areas in which few insecticides are used, are important safe havens for native bees in an environment in which there is increasing pressure on native bees from the chemicals used routinely in agriculture to fight pests. Preserving woodlots and the wild spaces that spring up at the woodlot edge is vitally important from a pollinator perspective, especially in agricultural areas, and pollinator habitat should be included as one of the many ecosystem services that woodlots and woodlot edges provide, both on and off farms.

Sue Chan

Sue Chan is the Program Manager and pollination biologist for Farms at Work. For more information on native pollinators and pollinator workshops, visit http://www.farmsatwork.ca/content/native-pollinators-program-3

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