2442Summary of Bombus/Bumblebee Records for BIML database
- Oct 7, 2012Note that dictation software was used in this message and thus odd word swaps can slip in!
Below are summaries of data for the BIML database for Bombus species. I realized recently that I did not the 2011 season and so I'm making up a bit for lost time. I have included any 2012 data that we have entered already. The bulk of 2012 remains to be entered over the winter.
The tables below include data only from states east of the Rocky Mountains. We do have a lot of data from national parks that will be entered at some point over the winter, but not much to add from previous summaries for 2011.
Table 1. Data for all species by state with all years combined.
Records by State and Year
Table 3. Totals by Species by Year
Table 4. Totals for just the regularly collected states of VA, WV, MD, DC
Table 5. Table 4 given as Percentages of Total Captures.
Ratio of citrinus/impatiens
OK, what follows are some thoughts on the totals above. Because this database reflects the specimens collected for a variety of projects, some of which collect intensively but only for one year or sometimes only for a week, it has to be seen in that context and is probably only a weak reflection of changes and trends over time. However, if you look at the last few tables which focus on collections made in the states we regularly collect in each year, these data present a better window into any possible large-scale changes in bumblebee populations that might be occurring. As such, one does not see large changes in the most common species. For example Bombus impatiens, griseocollis, and bimaculatus all have remained roughly the same in captures and occur roughly in the same proportions across all the years. While I have not done any statistics on this, and I'm a bit reluctant to do so because the problems of unequal sampling effort, there are some hints that there may be some things going on for a couple species. These are presented as strictly speculative, but it might be worthwhile looking at your own collection records over this time period to see if these patterns hold elsewhere. There is a possibility that these are an indication of some sort of large-scale change.
Of all the regularly collected species I would say that Bombus fervidus is one that potentially is showing a decline. Looking at the percentage table, found in table 5, you can see that the percentage across the past 10 years or so has undergone a decline that could be statistically significant. Again, there are plenty of problems with this data set as a measure of change but it may be an indication that something is going on, in particular, all the collectors involved always grab a Bombus fervidus when out collecting if one appears, so unlike some of the more common species it is certainly not ignored as being too common to collect. Thus, if anything, it would be over-emphasized in this collection compared to the common three species.
Recently Leif Richardson mentioned to me that he was surprised by how few Bombus citrinus they were getting in Vermont on their magnificent new survey (why are the other states not doing this?). He thought that it is perhaps an indication of lower numbers over the past few years. While we capture relatively few Bombus citrinus in our collections in looking at the patterns of change over time the ratio of Bombus citrinus to Bombus impatiens does appear to be decreasing and is a trend that people should be watching out for.
Any questions about the species or the verifications of records are more than welcome, we certainly have made mistakes in the past. I'm going to include the data set as an attachment in another e-mail. It may or may not come through due to size to some of your accounts so feel free to contact me directly if you're interested in the data set.
I should also mention that the demo database is a collection of many people's efforts and that we are always grateful for their contributions and their time.
Sam Droege sdroege@...
w 301-497-5840 h 301-390-7759 fax 301-497-5624
USGS Patuxent Wildlife Research Center
BARC-EAST, BLDG 308, RM 124 10300 Balt. Ave., Beltsville, MD 20705
The murmuring of bees has ceased;
But murmuring of some
Has simultaneous come,--
The lower metres of the year,
When nature's laugh is done,--
The Revelations of the book
Whose Genesis is June.