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Fight habitat loss: put a flower pot on every porch

We hear a lot about habitat loss, but what does that mean for pollinators? And what, if anything, can be done about it?

Habitat loss comes in many forms, but it can be divided into three major types: habitat destruction, habitat degradation, and habitat fragmentation. Let’s look at these one by one.

Three types of habitat loss

Habitat destruction is very much like it sounds: an ecosystem, which is a naturally-occurring assemblage of plants and animals and their physical environment, becomes obliterated. If you take a wild meadow, for example, cover it with asphalt and erect a shopping center, you have destroyed any trace of the natural environment and all the things that once lived there. Obviously, this is not good for pollinators nor any other living thing.

Habitat degradation is a reduction in the quality of an ecosystem. In other words, the land may still look like a wild land or a place where pollinators might live, but closer inspection will reveal that things aren’t quite right. An example is invasion by non-native plant species. If an area becomes overrun with say Japanese knotweed, kudzu, or Scot’s broom, the native plants gradually disappear. The native plants cannot compete with some of these invaders for sun, nutrients, water, or space. When the native plants disappear, the animal species that were dependent on them disappear as well.

Other things besides invasive plants can degrade a habitat. Industrial pollutants, pesticides, excessive shade or excessive sun, water diversion, or grazing animals can all degrade a habitat to the point that some of the original species can no longer survive.

The last one, habitat fragmentation, is perhaps the most insidious because it is deceiving. Habitat that is fragmented may look perfect, may have all the original components and none of the bad ones, but still be unfit for certain species to survive. How does that work?

An imaginary town

Let’s invent a town that is perfectly square, a mile per side. A square mile contains 640 acres. The developers of this town were forwarding-thinking individuals who decided to put a natural preserve at each corner of the town. Each preserve is 20 acres and left in a natural state. Sounds nice.

But these 80 acres are fragmented—fragmented because they are cut off from each other. Now, for some species this is okay. Even for honey bees this is okay, and maybe even bumble bees. Honey bees and some bumbles can cover the distance between the four preserves.

But for most bee species, this is a serious situation. Most bees can travel only a few hundred yards from their nest, so in small isolated areas like this, the species become inbred. The bees living there are cut off from the larger pool of genetic material because the only bees to mate with are the ones already there.

It doesn’t happen instantly, but when you have small, isolated, in-breeding populations, “bad genetics”—usually in the form of double recessive genes—begin showing up. Genetic problems arise more frequently in a closely-related population because there is a limited number of alleles (genetic variations of a gene) available. The situation only gets worse if no new blood is coming in.

If an inbred population is then confronted with an unusual circumstance, it may not have the genetic variability to survive. Unusual events like drought, extreme cold, a disease, or a new parasite may wipe out the entire population because it didn’t contain enough genetic variation to assure some survivors.

What island biogeography tells us about fragments

The study of island biogeography illuminates what happens to fragmented populations. Island biogeograhers examine populations that are cut off from each other. Remember Darwin’s finches? They presumably got dispersed to different islands, blown there by storms, and once there, each population developed different kinds of beaks because the food sources were slightly different.

That was a good result of separation, but more frequently the results are not so good. Small populations cut off from larger ones often do not survive.

From an evolutionary point of view, habitat fragments are like islands and the same processes affect them. Today, ecosystems everywhere are fragmented by cities, roads, airports, housing developments, farms, and industry. Fragmentation can even affect migratory animals like butterflies and birds because the fragments may be so far apart that the animals cannot find sufficient food or safe resting areas.

Wildlife corridors and how you can help

Maybe you’ve heard the term “wildlife corridor.” A wildlife corridor is a method of connecting various natural areas so that individuals can freely travel between them and encounter a larger selection of mates. Utility easements, for example, can be used as corridors by simply leaving them natural.

Individuals living in cities and suburbs can build corridors by planting wildflowers, keeping pesticide-free gardens, planting trees, and leaving a few weedy patches and some bare ground for the pollinators to use. While a single flower pot or a few milkweeds behind the garage may seem insignificant, they can make a huge difference. They give pollinators a way to connect with others, travel safely to other areas, and expand their genetic resources.

So do your part and plant that flower pot with something that blooms. Your pollinator friends will be glad you did . . . and so will you.

Honey Bee Suite

Flower pot with cosmos
One flower pot can make a difference. Pixabay photo.


Are we raising extra-large mason bees?

Except for natural bamboo tubes, it seems that most commercial tunnels sold for pollinator housing have an inside diameter of about 7 to 8 mm for orchard mason bees (Osmia lignaria), 6 mm for blueberry bees (Osmia ribifloris), and 5 mm for both alfalfa leafcutting bees (Megachile rotundata) and raspberry bees (Osmia aglaia).

I don’t know where these numbers came from originally—and that is what makes me suspicious of them. Everyone who cites these measurements got them from someone else, who got them from someone else. Much like that statistic that claims one-third of our food is pollinated by bees, everyone says it but no one can confirm it.

All I know for sure is this: when I give my Osmia lignaria a variety of tunnel sizes, they pick ones that are smaller than the recommended sizes. For example, they always choose a 5 or 6 mm hole over the much larger 7 or 8 mm holes. The summer masons and leafcutters seem to prefer a hole smaller than the recommended 5 mm, generally choosing a 4 mm hole.

If you’ve been around honey bee keepers for a while, you know there is heated debate about the size of artificial foundation. On average, the cells in most foundation are quite a bit larger than the cells found in natural combs, and larger foundation produces larger bees. Many people, myself included, think that a natural cell size is best for overall honey bee health.

Now I’m wondering if we are creating artificially large Osmia and alfalfa leafcutting bees by providing housing that is a little bit wider than that found in nature. Furthermore, we know that wild species raised in artificial nests are falling victim to ever more diseases and parasites, just like honey bees. Are any of these ailments more apt to appear in larger bees raised in larger tunnels?

Just as an experiment, I purchased a pair of these: Kinsman Giant Solitary Bee Nester with 60 Tubes. The tubes inside are about 7 mm in diameter. Next I bought a supply of Paper Straws ranging from about 4.5 to 7 mm inside diameter. I made collars for the paper straws so they wouldn’t float around inside the larger tubes.

When that was done, I set the first Kinsman nest on top of another pollinator unit behind my house, just to get an idea of how to fasten them together. I went to get some hardware, but by the time I got back, the mason bees were already investigating the smaller holes. I decided it was too late to move it, so I just tied it on with survey tape. I will set out the second nest in about six weeks when the summer masons and leafcutters are flying.

My plan is to remove the cocoons in the fall and look for differences between those in large tubes vs those in smaller tubes: pollen mites, mummies, parasites, whatever I can find. This is by no means a controlled experiment, but just a look-see to decide if there is something to study in the future. I will keep you posted.


Some of the paper straws I used. They come in different diameters, but you have to read the fine print to find the info. I got different colors so I can easily tell the sizes apart.
I measured the straws and cut them to the right length for the nest.
I slit the tubes to make them easier to open later. They pop back into shape after they are cut.
I put the slit straws into larger ones so they maintain their size.
I used the cut pieces as collars for those with too much free space around the tube opening.
Here is a larger straw with a collar in place.
Here is a Kinsman nest being filled with straw inserts.
Within five minutes of putting it outside, the masons were inspecting it.

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Knotty but nice for bees

Okay, we all know that Japanese knotweed is an invasive species, prone to tearing up your driveway, cracking your foundation, and choking rivers and streams. But what’s the best thing about knotweed? That’s easy: it’s in bloom. Right now. Right at this very moment when no other plant is even thinking about it.

Japanese knotweed, Fallopia japonica (formerly Polygonum cuspidatum), is an herbaceous perennial in the buckwheat family, Polygonaceae. Many people think it is some kind of bamboo because of its hollow stems and raised stem nodes, but it has no relation to true bamboo, which is actually a grass.

The World Conservation Union lists Japanese knotweed among the top 100 worst invasive plants. But if you can look past that detail, it is actually a pretty plant with large spade-shaped leaves and showy cream-colored flowers. The plants may grow 5-8 feet tall in a dense, bush-like display.

At this time of year in western Washington, you can hear these bushes before you see them. They are alive with pollinators and are particularly attractive to honey bees. Many beekeepers manage to harvest a monofloral honey from the vast stands found locally. And if you don’t harvest, it makes a great late-summer boost to a colony’s winter pantry.

The honey is dark and flavorful, and many people compare it to a mild form of buckwheat honey. I’ve tried it and, personally, I don’t taste a resemblance. Still, it is good and definitely worth a try—you can often find it sold as “bamboo honey,” especially on the east coast. The sample I had crystallized quickly at a rate similar to buckwheat honey.

Bee lovers have found another use for Japanese knotweed. The hollow stems are often cut into lengths and bundled for use as native bee habitat. The stem diameters vary just enough to provide suitable housing for a wide range of tunnel-nesting bees, including mason bees and leafcutters.

The pictures below were taken in Kirkland, Washington yesterday afternoon. The owner of this invasive marvel says, “Standing next to the knotweed almost sounded like you were standing next to a hive.” She also said, “I hear knotweed is invasive and hard to get rid of. My side yard looks like I’m growing knotweed as a crop. Neighbors have the same.”

Yup, sounds like knotweed. After it conquers the yard it will conquer the house. Once the flowers die back, she should cut up the stems for native bees and get rid of the rest.


The honey bees are having a fine time in this residential crop of knotweed.
A honey bee and a fly share a late-afternoon sugar fix.

Pollinator walls, bee towers, and insect hotels

It seems that everyone is building for the bees these days, from private citizens, to transportation departments, to architectural design firms. The proliferation of bug structures, no matter how humble or how grand, indicates that humans are finally getting it: insects need a place to live too. As we cover more and more of the earth’s surface with buildings, roads, airports, and crops, it becomes vitally important to provide living quarters for the insects that serve us.

The structures are as varied as the insects that inhabit them. They may be smaller than a birdhouse or may cover the side of two-story building. They may be designed to attract bees, potter wasps, other pollinating insects, or even vertebrate pollinators like hummingbirds and bats. Some offer housing to non-pollinating beneficial insects such as ladybugs and lacewings. The options are endless and the designs are original and creative.

Germany seems to be the leader in bug structures, followed closely by Great Britain. Because those countries are small compared to places like Canada, the United States, and Australia, they were quick to realize the importance of coexisting with the beneficial insects and the need to provide shelter for them in the built environment. The insects use the habitat for shelter, safety, nesting, raising young, and finding food.

A feature that distinguishes walls, towers, and hotels from structures like mason bee condos or bumble bee nests is the wide variety of nesting choices. Pollinator walls may contain hollow reeds, wood with pre-drilled tunnels, cracked or drilled masonry, straw bundles, rolled corrugated board, clustered stones, or dry leaves. The “invertebrate habitat” shown below was built by the Cheshire Wildlife Trust. It contains many types of habitat and was built completely from recycled materials.

Invertebrate Habitat by Cheshire Wildlife Trust

The next photo shows the winner of the 2010 Beyond the Hive Competition in London. This “bug hotel” was built by Arup Associates and is designed to encourage many types of invertebrate inhabitants.

Insect hotel by Arup Associates.

If you decide to build your own habitat, here are some important issues:

  • The structure should be in an area sheltered from bright sun and high wind, such as close to a building or under a shady tree. If you hope to attract some native bees, at least past of the structure should be in the sun.
  • Insects need water, so a reliable supply such as a pond or creek should be nearby. Alternatively, you can provide an artificial source–just don’t let it run dry.
  • Many solitary bees and wasps need a source of mud.
  • The fill material should be varied in type (stones, masonry, dead leaves, reeds, wood, twigs) and have many little cracks and crannies, nooks and crevices.
  • The design must be structurally sound so it doesn’t topple from wind, rain, or snow. If you live in an earthquake zone, keep the structure low and wide instead of tall and narrow.

Structures don’t have to be large. The one shown below is small enough to become part of the garden. This was an entry in the Beyond the Hive competition by Helaba Landesbank Hessen-Thueringen.

Small but effective.

The possibilities for building insect habitat are endless and can satisfy the artist in you. So give it a try. If you like, send me a photo and I’ll post it here on my site.

Pollinator housing attached to a building. Photo by Wildbienen.


Occupy the barren landscape

When we think of bee forage, we usually think of vegetable plots, row crops, orchards, hedgerows, flower gardens, and meadows. But some of the best bee forage in the world comes in the form of trees—not only fruit trees—but trees like maple, chestnut, willow, basswood, locust, and alder. Some species provide only pollen, some only nectar, and some both, but in any case they are important food supplies for both honey bees and wild bees.

Unfortunately, treed areas are becoming scarce. In the southeastern United States, coal mining operations flatten mountains in order to extract the coal. Mountaintop removal, as the practice is called, leaves bees with nothing to eat for acres in all directions. Local trees such as sourwood and tulip poplar, along with native shrubs and perennial flowering plants, are typically replaced with non-native grasses that do nothing for bees.

Here in western Washington, our Department of Natural Resources routinely sprays new plantings of Douglas-fir with herbicides designed the kill the maple, alder, elderberry, bitter cherry, and cascara that normally appear in newly logged areas. The purpose, of course, is to give the “economically important” species a head start. But it seems short-sighted. Instead of a healthy recovery with multiple species in a complex habitat, you get the same type of monocrop seen in agricultural areas—with similar problems.

As I hike the state forests, I’m amazed and distraught at the number of warning signs posted by the DNR which list the panoply of herbicides that will be (or were recently) sprayed. Not only do I think it’s an unnecessary and questionable practice, but I wonder that any state so deeply in debt can afford to purchase and apply all those expensive chemicals. Surely there’s a better use for public money than poisoning the land while making the rich corporations even richer.

We beekeepers need to spend less time blaming each other for trivia (you should/shouldn’t feed sugar, you should/shouldn’t stop swarming, you should/shouldn’t provide ventilation) and go after some of the serious problems we have as a nation. We need to occupy the stripped mountains, the clear cuts, and the monocrops until we make our voices heard.


Mountaintop removal = bee removal. Photo by Ohio Valley Environmental Coalition.