More Graphs!

In my previous post I compared last year's butterfly records with the average for the previous five years.

I then realised that back in 2001 I had a job as a seasonal countryside ranger at John Muir Country Park, here in East Lothian. I used to keep a record of the butterflies I saw each day and I also walked a transect. So, I thought that it would be interesting to compare my 2001 records with the last five years.

I know it is not very scientific to compare the results of one person from one site with those of several people from all of East Lothian, but nonetheless I have noticed some interesting results.

These first few graphs don't show anything too remarkable ...

... as I expected saw fewer butterflies than the current 20 or so recorders, although I was outside all day five days a week. However, what I notice is that my records from 2001 appear to be about two weeks later than the average over the last five years. John Muir Country Park is coastal and well known for its sunny weather, so if anything I would expect butterflies to appear there earlier than much of the rest of East Lothian.

Could this possibly be a sign of climate change?

The Green-veined White seems to be a remarkably consistent butterfly. Year on year its numbers don't appear to change much.

And I was interested to see how few Large Whites I saw. They certainly seem to be more common these last couple of years than I remember them being in the past.

The Red Admiral has certainly become more common over the last few years. It now appears to be able to survive the winter here, but in 2001 I didn't see any until the end of June.

And I had the impression that there are fewer Small Coppers around these days than there used to be. My records from 2001 appear to confirm this.

The Small Heath intrigued me when I worked at John Muir Country Park. They appeared to have a very much shorter season there than elsewhere in East Lothian where I was surprised to see them several weeks after they had finished at John Muir Country Park. Checking the more recent records, from 2010 Small Heaths appear to have a much longer season. It makes me wonder if they used to have one generation a year, but now can manage two.

The Small Tortoiseshell used to be a very common butterfly, which has declined quite seriously in numbers over the last few years. It is amazing to see how many more there were in 2001.

In contrast it appears that the Small White is more common these day than it was back then.

I also notice that back in 2001 I didn't record any Commas, Small Skippers, Speckled Woods or Wall Browns, as they hadn't arrived here then. In 2001 I didn't record any Painted Ladies, either, although I do remember seeing several in 2000. So, 2001 was obviously not a year when they arrived here in large numbers.

I was wondering if my mind was playing tricks on me, but my recollections appear to be backed up by the figures. What we can't be clear about is the cause of these changes. It is easy to jump on the climate change bandwagon, but it might just be the cause.

I promise, there will be no more posts containing graphs this year!!

5-Year Comparisons

I have mentioned in my previous couple of posts how things have changed for Speckled Woods and Wall Browns over the last five years in East Lothian. These two species have both extended their range northwards and only arrived in the county within the last ten years.

I have been comparing 2017 figures with the previous four years for all of the species occurring here and it is apparent that some species have done very much better than others. I had my own perceptions of how well each species had done, but it is interesting to see the combined records from all of the volunteers.

The problem with doing a comparison like this is that each year I have had more people send in their records  to me, so you would expect to see more records for each species. However, this hasn't been the case with many of them.

For instance, when looking at the Large White, Small White and Green-veined White, there is a marked difference in how they did in 2017. These three species that share very similar life cycles, with a spring generation and a summer generation. It is odd that the Small White apparently had a poor second generation, but the other two species did as well as ever.

In the graphs below the red line shows the 2017 records. The blue line is the average figure for the last five years.

I had thought that there had been fewer than normal  Peacocks around in 2017, but when I looked at the records received they appeared to have done better than normal.

This is in contrast with the Small Tortoiseshell, which seemed to have a very poor year. I was surprised to see that there were more records than I expected.

2017 was an amazing year for Red Admirals. They have been increasing in numbers over the last few years and it is thought this is because they are now able to survive the winter in the UK. Whether this is because the temperatures are warmer than in previous years, or if they have adapted to our climate is unknown. It will be interesting to see how the very cold winter we are experiencing just now will impact on their numbers later this year.

What I find most interesting is that the species, such as the Wall Brown, Speckled Wood and Small Skipper, which have all moved into East Lothian in the last nine or ten years, have continued to increase in numbers, while some long-established species have been declining.

Most people who submit butterfly records to me it was felt that 2017 was a poor year for butterflies. As I mentioned previously we may be showing a falsely rosy picture of how the butterflies did, as we had more people sending in records. However, the differences between the species is valid. 

It will be interesting to see what happens in the years to come.