Butterfly statistics

view of a Male Common Blue nectaring on a white flower with wings fully open
Common Blue. Photo: Michael Skelton

We are seeing some interesting statistics coming out of the butterfly sightings reported to this website.As of 6 August, the total number of butterflies recorded on this website was 39,142. Our highest ever figure for the entire year was 37,841 in 2014.Graph showing numbers of butterflies each year

The species of butterfly being reported are interesting, too. The graphic showing species reported in the last 10 days shows the top ten as below:

  1. Common Blue 654
  2. Meadow Brown 411
  3. Gatekeeper 381
  4. Small White 213
  5. Speckled Wood 159
  6. Brown Argus 115
  7. Large White 110
  8. Green-veined White 86
  9. Small Heath 83
  10. Red Admiral 78

It would seem unusual to have a blue coming above either of the most common browns, though this may say more about the Meadow Brown and Gatekeeper finishing early, and for the Brown Argus to be in the top ten is surprising: the total for the whole of 2017 was 152.

Side view of butterfly with orange and black markings on a pale brown background

Brown Argus. Photo: Mark Pike.

These are only musings on the current figures: we will not know what sort of butterfly year we have had until the full year’s statistics are analysed. The website results are not statistically valid: the amount of recording effort, and the conditions under which the sightings were made are not controlled, which is why we also have the transect walk approach to give us a more meaningful figure. It could be, too, that the way we record butterfly numbers nationally, in five-year cycles, may have its effect: 2014 was the end of a five-year period, so we were exhorting people to record as much as possible at that time.

2018 is the penultimate year in the current recording cycle, but hopefully our pleas to help us fill ‘white holes’ (places where no butterflies records have been sent to us in the five-year period) are having some effect now as well, especially as we have our superb nearly-real-time white holes map.This shows which species have been recorded in each kilometer square in Dorset, so you can not only see places where no butterfly sightings have been made, but also places where few species have been recorded, allowing you to target your efforts to best effect.

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