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The Second Time Around Isn’t Always Lovelier

Posted: July 13, 2013

Sometimes we have no choice but to accept year-to-year variation
Bee foraging garden inside the Grozinger Lab's hoop house.

Bee foraging garden inside the Grozinger Lab's hoop house.

This summer, I am repeating last year’s field work, incorporating a few modifications, with the hope that I will more efficiently produce an equally significant dataset as last year and be able to strengthen my findings. But because field work is largely unpredictable, my expectation that things would work out perfectly for two years in a row has fallen a bit short.

My work involves observing bumble bee pollen foraging behavior to native perennial flowers. My undergraduate assistant Bekki and I count how many bumble bees visit each plant species and how long they stay collecting pollen from each species. Most data is collected at our hoop house, a large foraging arena that restricts my bumble bees to only the flowers provided to them. From this data, I can calculate the bees’ foraging preferences. By collecting continuous foraging data throughout the day, at least until all the pollen has been depleted, I can see finer scale changes in foraging preferences that other research in the field has often failed to report.

In 2012, the data collection went very smoothly. We had an early spring and the weather was consistent every day so that we could follow a standard schedule of work throughout the entire season. Most of my flowers bloomed early so that we were able to produce a large dataset of bee foraging behavior. It was a dry and sunny summer so the bees routinely foraged every day at the same rates, since no rain, wind, or clouds effected their foraging.

However 2013 has been a different story. But maybe the weather this year is more typical of a Pennsylvania summer. This spring, our plants emerged quite early, leaving me hopeful that I would expect blooming to occur around the same time as last year. However, with the cool spring and consistent rains, blooming occurred almost 3 weeks later than last year! What is exciting though, is that where only 7 of the 9 of my plant species bloomed last year, all 9 will bloom this season. Strangely though, some individuals of a few plant species started showing signs of blooming, where others have yet to advance beyond the vegetative state. I hope they will bloom too! I’ve also had some troubles with my bees. We order our colonies from a commercial bumble bee breeder, and ask for colonies that are in an early stage of development. However, the workers of one of our colonies killed their queen, and we noticed two more days in a row two more killed queens. How this occurred, we are not sure, but we imagine that the colony was at a later stage of development where they start producing new queens, which would usually occur in August. Our other colony, since its introduction into the hoop house last week, has quickly taken up the behavior of “robbing” flowers. Though not a common practice for naïve bees, when bees are in a situation where forage is limited, robbing (purposefully damaging flowers to access nectar or pollen) can occur and is quickly learned by other bees. This behavior can be irreversible.

But there is good news, even with the unpredictability of the weather, plant phenology, and bee behavior, data collection is underway. I have many flowers still waiting to bloom and new bumble bee colonies are being delivered. The problems I have encountered this season should be expected by anyone conducting field work and should not be discouraging. If anything, we learn from field work all the variables that can influence our study system—the factors we get to avoid in the lab. Our ability as researchers to encounter and creatively design projects and solutions that can account for these variables will strengthen our results and help us understand nature on larger special scales.

I hope you look forward to my next update during the week of August 18th.

--Anthony Vaudo (8 July 2013)