Sunday, 4 May 2014

Spring data

April has passed and a considerable number of photographs have been taken, creating the biggest block of photographic data for this part of the year (Figure 1) that the HRS has assembled. Two points can be recognised. Firstly, the contribution of the UK Hoverflies Facebook group has been very significant. Secondly, that numbers of records derived from Flickr and iSpt etc have held up, despite the shift towards Facebook where several of the most active photographers now post their shots
Figure 1. Five-week running means of photographic records for the years 2011 to 2014, with the 2014 records represented as all records and a sub-set from sources other than Facebook (the situation that obtained before 2014).
The two trends offer a very positive indication of growth in hoverfly recording, which is very encouraging. It helps to show that the strategy that Stuart and I embarked upon five years ago is paying dividends. At the time, we were concerned that recruitment of new recorders was pretty low and that we were not connecting with people. That point represented a watershed between the traditional recording scheme and society-based approach to engagement, and more pro-active approach using 'virtual societies' where we set out to make contact by engaging locally. Our training programme has certainly had this effect and the internet has greatly expanded the basis for recording. Translating this into the full-spectrum recording that the old guard of the HRS have done may take a while longer, but even if only 5% of enthusiasts buy a microscope and start to look at preserved specimens we should replace the old guard with a new generation!

I think that the community of photographic recorders may also be extremely helpful in developing knowledge about yearly changes in phenology amongst more abundant and obvious species. This could be extremely interesting if developed as long time-series data. By way of example, two graphs are indicative - the first being a selection of spring species (Figure 2) and the second specifically Epistrophe eligans in 2014 (Figure 3).

Figure 2. Five week running means of combined photographic data 2011-2014 for a selection of spring hoverflies.
Figure 3. Numbers of photographic records of Epistrophe eligans in spring 2014 - data to 4 May and consequently incomplete.
The  data for spring species are combined for 2011-2014 and have been smoothed by a five week running mean. I will look in more detail at individual year data but everything is a bit skewed by larger numbers of records from 2014 and much more limited numbers in some years. I have simply posted the data for 2014 for Epistrophe eligans because in past years this species has not figured greatly in photos. The graph will be updated at some point because this species' flight season is not over. The trend is obvious though!