Dead bees and crow roosts

It is December 22nd, the first full day of winter. I always look forward to this day because from now on the days start getting longer.

In any event, I spent the day in New York State “paying the rent” and visiting with the landowners who allow me to keep bee yards on their property. On the 19th we had a major snow storm here on the East Coast and at my home  in Hampton, CT, we got about 16 inches of snow. Out in Dutchess County NY they got only a couple of inches. I took the time to visit a couple of yards just to look around and see if any bees were trying to fly. The temperature was 25 degrees F and the sun was shining. As expected, I watched a few bees leave the warmth of the winter cluster and fly a very short distance away from the hive, only to crash land on the snow and shortly thereafter, die. I keep ten hives in each yard and the snow was littered with dozens of dead bees. Healthy honeybees do not defecate in the hive, they usually wait until the weather is  warmer than 50 degrees and then will leave the hive to void their feces. In years past, I thought that this was what was causing the dead bees, even on cold days. The  bees , it seemed, were trying to take a cleansing flight and couldn’t make it back to the hive. However, there were none of the tell-tale yellow and brown spots that would have indicated a cleansing flight. I predicted that when I got home there would be calls from beekeepers who were wondering what was going on with thier bees. Sure enough, there was one phone message and one email wondering why bees were leaving the hive to die and hinting that something mysterious was happening.  This has nothing to do with CCD or any other malady. Here is what is going on.

I  recently read a book called Winter World by Bernd Heinrich. He is a well respected biologist, author, professor, endurance runner, beekeeper, the list keeps on going. One of his fields of expertise is in thermoregulation. Not just in insects but mammals, birds, turtles etc. In this book he talks about how organisms survive in the temperate winter and in one chapter writes about just this subject, why bees fly in winter.  He goes into great detail describing the methods he used in determining  that quite often the bees that are flying at low temperatures are actually leaving the winter cluster to look for sources of nectar or pollen!  He discovered that the cleansing flights actually took place at higher temperatures and involved much larger numbers of bees. His conclusion was that even if these foraging bees never returned, they were individually expendable due to the value of fresh food to the colony if some of them ultimately did find a  food source.

This makes sense to me when you consider that the older bees are the ones who would be leaving and they probably would perish before spring anyway. Some times there is a thin line between winter survival and starvation. It is surprising how early in the late winter we can see some bees returning with pollen on their hind legs. It is well known that bees finding skunk cabbage flowers in March are able to warm up in the protective spathe  that surrounds the flower. The temperature is several degrees warmer than the outside air. These plants are able to push up through ice in order to blossom.

In another of Heinrich’s books  “In a Patch of Fireweed” he has a series of  chapters dealing with how wasps and bees warm up and stay warmed up in order to forage. One chapter deals with swarms and how the bees regulate the temperature of the cluster. Its too involved to go into now, but the common idea that the out side or “mantle bees ” change places with interior bees in order to warm up is just not true.

Another essay in “Winter World” deals with winter roosts of crows. Two of Heinrich’s passions are Crows and Ravens. He wondered where and why crows roost at night. He discovered a large crow roost, not deep in the woods, but instead near a brightly lit shopping center!  There were thousands of crows flying for miles to roost in the trees in a well lit area. He determined that the crows were roosting there to avoid one of their most feared predators, the Great horned Owl (another passion of Bernd Heinrich, he once rescued an owlet after a late snowstorm and kept it semi domesticated for two years until he was able to integrate it back into the wild).

While I was returning home from New York tonight, I was driving on I 84 through Hartford CT as the sun was setting. There were hundreds of crows flying to roost in a group of trees in the west side of the city. It is near the former Xerox Building right next to the highway, another well lit area similar to the one Heinrich talks about. As I drove through the rush hour traffic in Hartford, I could see a steady stream of crows headed in that direction. I continued to see them all the way to East Hartford and the Manchester line, at least ten miles “as the crow flies”!  Several years ago, not too far from the crow roost, there was  (and maybe there still is) , a large European Starling roost under the highway bridges near the Hartford bus station.  These birds also form large winter flocks not only for feeding but also for roosting.  I don’t think that these flocks are for sharing warmth as much as for spreading the individual risk from predators over a large population. The individual bird, in this case, would be less likely to be taken by a predator than would one bird sleeping alone.

It never ceases to amaze me how organisms deal with the cold winters in the temperate regions. My friend Glenn has a very simple way of dealing with the long cold nights here in New England. He borrowed my copy of Winter World and went to Hawaii for the winter.  He says he will return with the Warblers!

Adam Fuller