cleptoparasites and host bee population dynamics II
James Cane
Greetings again. Here I propose the simplest of methods for estimating relative cleptoparasite abundance at a nesting aggregation. I wanted something simple, as over the years, most aggregations that I have encountered were not intentionally sought, but rather serendipitous encounters while engaged in some other project or on a hike. As a rule, I don’t carry a quadrat frame, a cage or a meter tape reel when I hike. I often do have a killing tube, a pocket writing pad, a pencil and sometimes a hand net. Maybe you do too.
What I suggest is to obtain a relative ratio of cleptoparasites to nesting host bees on an active nesting aggregation. Simplest would be counting each for some duration of watching. I once instead used the frequency of crossings by flying bees as they flew over a string stretched across the aggregation, but that could severely constrain sample sizes. As a rule, should of course choose good bee weather and note that females are returning to nests with pollen loads (to be certain that cleptoparasites have emerged for the season). Record the numbers of flying female bees and patrolling cleptoparasites and set a reminder to return in a year to repeat, as really the changing ratio will be more informative.
I will be away the rest of the month, but don’t be shy about voicing considered modifications to this method. For one, more cleptoparasites may be airborne over the aggregation than host females, who simply dart into their hole. I believe that should be something of a constant from year to year, but maybe not between different cleptoparasite species. Don’t count males, as their ratio will shift sharply during the nesting season. Maybe our visual biases will skew the result...do we more readily see host bees or cleptoparasites when generally watching an aggregation? Maybe it would be better to carry a string knotted to mark 4 corners of a square or rectangle when pinned out with 4 little nails or golf tees, then just counting activity in that square. It would not be bothersome to just keep that in a day pack during the field season. But would it be a decided improvement? For sure I would keep track of the time spent observing, as it might find use.
With enough participants for say 5 years, I believe that meaningful insights could be gained that are currently not available regarding aggregations and how often they endure or succumb to cleptoparasite depredations.
Yours, jim
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