The post earlier this week on the question of “Why do bumblebees follow ferries?” generated quite a few comments, both on the blog and on Facebook. As I’d hoped a number of people have chimed in to say that they have observed the same thing, or commented that they often see bumblebees when sailing or kayaking out at sea.
Here are the additional observations in increasing distance order to nearest larger area of land. Distances are approximate and in some cases it’s unclear where exactly the observations were made:
Isle of Mull to the Isle of Staffa: 6.5km
Skye and the Outer Hebrides going in both directions: 24km
Ferry to Jersey: 28.4km
Estonia to Helsinki: 80km – described in a short paper by Mikkola (1984).
However this is nothing compared to evidence that queen bumblebees may engage in mass migrations (involving thousands of bees) across the North Sea from England to Holland, a distance of 165km! See Will Hawkes’s short article “Flight of the Bumblebee“.
This idea of mass migration is new to me, though the Mikkola (1984) paper cites some earlier literature on the topic. And this morning I had a quick phone chat with Dave Goulson who tells me that he occasionally gets people contacting him to tell him about such events. But it’s unclear why these bees should be flying such large distances, how they coordinate their migrations, or indeed how much energy they need to store to travel that far. In addition there are implications for gene flow between British and Continental subspecies of bees such as the Buff-tailed Bumblebee (Bombus terrestris). Even a relatively well studied group of insects such as the bumblebees can continue to surprise us with new questions!
Thanks to everyone who contributed observations and ideas, it’s much appreciated.