These plots got me thinking about how the numbers work in terms of yearly contributions and the numbers involved in the HRS, year on year. Today, the total number of contributors exceeds 8,000 names going back to the 19th Century. I suspect that there will be some duplication where people use multiple aliases that I have not detected, but I doubt that this is significant. In recent years, the number of contributors has exceeded 1,000 individuals per season, but until the advent of the Facebook group many of these would have been single records from a photo posted on Flickr or other hosting systems. In the last couple of years the number of contributors has dropped quite markedly because I no longer find it time-efficient to search Flickr during the winter. So, the numbers of single entry contributors have dropped.
In order to get a feel for what is happening I assembled the data in three ways:
- the number of recorders in each year who, between them, contributed 50% of the data for that year;
- the total number of contributors in each year; and
- the average number of records per contributor.
|Figure 2. The number of recorders whose combined efforts generated 50% of the records in a given year between 1975 and 2016.|
|Figure 3. Total number of contributors in each year between 1975 and 2016.|
|Figure 4. The average number of records per contributor between 1975 and 2016.|
In the 1970s and early 1980s records came from a very narrow spectrum of Dipterists, most of whom would have used microscopes and specimens and would either have relied upon Coe's key or possibly test keys for the first edition of Stubbs & Falk.
The publication of Stubbs & Falk led to an increase in recording activity and the arrival of a small number of very active recorders whose contributions meant that the average number of records per recorder jumped quite markedly. Several of that cohort continue to be active to the present day, with recruitment of new recorders relatively constant at around 12-15 new people per year until around 2006. This is the point in the process where Stuart and I started to ramp up our training programme and I think there is some evidence that it has had an effect. This also about the point where digital photography started to gain popularity and a new cohort of photographic recorders entered the system.
By 2008, the impact of digital photography is pretty clear. We cannot claim the rapid growth in contributors to have resulted from our courses. At best we have trained about 500 people in the past ten years and I would be amazed if more than 20% of trainees ever go on to do any serious recording (probably many fewer). So, the real changes have come from the advent of iSpot, Flickr and, latterly, the UK Hoverflies Facebook group.
The dip in the average number of records per recorder around 2011/2012 coincides with the period of greatest activity by me scanning Flickr for photographs that could be converted into records. Lots of single record recorders were created as a result. Meanwhile, the climb in the average over the following four years suggests a substantial change in the composition of the community with many more people making a serious effort to record hoverflies and to post their findings on the Facebook group. We can see this in the steep rise in the number of contributors making up 50% of the incoming data.
What is perhaps less obvious is that there are vastly more people who contribute 100 to 500 records per year. Figure 5 reveals just how this cohort has changed, and it is clear that the UK Hoverflies Facebook page has had the most dramatic impact on recording.
|Figure 5. The numbers of contributors of 100 or more records in each season from 1975 to 2016.|