Thistle Bumblebees

4 bumble bees

Can you spot all 6 bumblebees in this picture?

Although I have mentioned many times that honey bees are not going extinct (there are actually more kept hives of honey bees today than 10 years ago), I am concerned about wild and native species of bees. Loss of habitat, climate change, and pesticides are terminating many of them. So I was delighted to see a nice population of bumblebees tirelessly working the wild thistle which we allowed to grow on the edge of our flower garden.

Over a period of ten days, the bees were on the thistles steadily from about ten until dusk. We would see about 6 or so on the 14 heads of thistle near our deck at any one moment. They were busy flitting about, so it was hard to really know the full number – but I would guess that several dozen (probably from the same clandestine nest) were coming and going. I finally decided to film them so I could get a better count and watch their activities over and over again in slow mode.

2 bumble bees niceOn my video, I counted as many as 7 in view at any one moment, sharing but not apparently competing for the same 14 thistle heads. Each individual spent an average of 18 seconds on each flower. An old-time beekeeper once told me that if a bee (he was talking honey bees, of course) spends more than 5 seconds on a flower, then the flower has little nectar as it is taking the bee too much time to search individual florets and get a fill. I don’t know about that for sure, but I have seen bees on citrus and sweet clover flowers (which are each tremendous honey plants) take about two seconds to fill up. In the case of the bumblebees on our backyard thistle, the bees spent a few seconds in one position, then moved on the same flower and continued.

Interestingly, there was very little pollen on these workers’ corbiculae. This could be because so many bees are working the flowers that the pollen production rate doesn’t keep up with the foragers. Or it might be because it is getting late in the season and the bumblebee nest contains fewer larvae needing pollen, hence most of the collectors are going after nectar. Or there are other reasons – I don’t know. All I do know about this is that I was glad to see the busy bumblebees and encouraged that at least this one species has found something nourishing in our yard.

About Ron Miksha

Ron Miksha is a bee ecologist working at the University of Calgary. He is also a geophysicist and does a bit of science writing and blogging. Ron has worked as a radio broadcaster, a beekeeper, and Earth scientist. (Ask him about seismic waves.) He's based in Calgary, Alberta, Canada.
This entry was posted in Ecology, Honey Plants, Save the Bees and tagged , . Bookmark the permalink.

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