Stems from the invasive knotweed have been cut down to provide nesting sites for native bees.
The European honeybee was imported into north America in 1622, very early in the colonization of the continent by Europeans. Over the four centuries since it was brought here, the species has thrived not only in cultivation, but also as feral colonies started by swarms that escaped from managed hives. At the same time much habitat used by native bees has been lost.
There are about 4000 species of bees native to the US. Many of these are solitary, that is, they don't live in colonies but rather lay their eggs individually in the ground, in holes in wood, or in hollow stems. They include species of sweat bees, carpenter bees, and many others. Most of these bees are non-aggressive; many cannot sting, and those who can generally only do so if they are directly threatened, for example if they are stepped on. They pollinate all kinds of plants.
Just as interest in native plants has increased because of their potential for supported a more stable and complex landscape, so too has concern about the loss of native insect habitat increased. There are a number of things we can all do to promote the health of native insect communities.
Many of these bees overwinter in plant stems while they are still on the plant or after they have fallen to the ground. Blowing or raking flowerbeds disrupts the homes of insects. Obsession with neat and tidy flowerbeds results in significant loss of habitat. Lazy gardening is beneficial to wildlife!
The sprays used to kill adult mosquitoes also kill bees, butterflies, beetles, and other insects. Consider alternatives to broad spectrum insecticides when controlling mosquitoes.
For his Eagle Scout project Ansel Nathanson built a lovely bee habitat for the trail. He used cedar in constructing the support and the frames are removable so that we can change the stems every couple of years to keep things safe for the pollinators. Follow the link above, as well as the resources below, to learn how to create bee habitat in your yard.
For more information about building habitat for native bees, try these sources:
https://pollinators.msu.edu/sites/_pollinators/assets/File/Building%20Bee%20Hotels.pdf
This video shows a bumblebee getting pollen from a native rose flower on the trail. You can hear lots of bees in the background but the loud buzzing sound is coming from the bee that is excitedly moving around in the rose. The buzzing actually helps to dislodge the pollen so the bee can more easily gather it up. If you pause the video at 7:31 or 8:41 (seconds) you can see the gobs of pollen packed onto the back legs of the bee. While adult bees use flower nectar for energy to fly around, the high-protein pollen is absolutely required as food for proper growth of bee larvae—the baby bees.
There are many roses in the new meadow areas of the trail. Later on the bee-pollinated flowers will produce sweet red fruits called rose hips, which are relished by fruit-eating birds like robins, waxwings and catbirds.