Thursday, 12 August 2010

Butterfly transects

Transects, or fixed-route walks, are invaluable in the study of population change, but as was illustrated today, the rules have to be followed for the information to be useful.

Last year I walked an hours' transect counting butterflies on the grassland of Tolsford Hill, in late May and late July. This year, the bad weather in spring kept the temperatures down, giving me a (poor) excuse not to get out, and various commitments have deferred the counts until now - mid-August.
Although the weather was similar on 31st July 2009 and 11th August 2010, the numbers and species of butterflies recorded were very different.
Common Blues were by far the biggest increase, with 116 counted, compared with 10 last year - because of the time difference, however, it is not possible to conclude that this represents a real increase (although it has been reported that the second emergence has been strong this year.

... a recovery in the number of Small Tortoiseshells, with nine seen, against none last year;
....more Small Coppers and some late skippers.......

... fewer Gatekeepers but more Meadow Browns, and no Painted Ladies or Clouded Yellows this year. It was good to see a similar number of Wall Browns to last year's result, which were very scarce in the cool spring. The grassland (which is partly sheltered from the westerlies) is clearly a favourable habitat, and at this time of the year benefits from clumps of Marjoram and plenty of Small Scabious.

An adjacent field seemed to have a promising headland, and a quick look confirmed that there was a good selection of arable weeds, including Corn Mint and even the two Fluellens.

Elsewhere, searches for Grayling at Folkestone again drew a blank, but did reveal three each of second-emergence Dingy Skippers and Small Blues;.... while Kingsdown's rifle range also still holds Small Blues, and a white moth that should be called Brown-veined Moth but probably isn't [no, it's a Sulphur Pearl sitochroa palealis].

A Kestrel stood steadfast on the path, not moving until approached - I'm sorry, but it was on the path. It seemed to fly strongly enough so there's no obviously explanation for its behaviour.

And at Restharrow Scrape, a Partridge family of thirteen tries to evade the attentions of some crows.


Greenie said...

Steve ,
Your Common Blue findings seem to be replicated all over , it has been a very good second brood .
And a good year all round underlined by Dingy Skipper and Small Blue second broods .
Great news on the Small Tortoiseshells .
Can't remember the last time I saw more than 2 Grey Partridge , never mind 13 .

Warren Baker said...

Very interesting post Steve. I can confirm with even my meagre butterfly counts that Small Copper, Common Blue and Small Tort. have increased this year :-)

Anonymous said...

I think that the moth is Sitochroa palealis which is a
fairly scarce moth of the south coast.

Kingsdowner said...

Thanks for moth ID, Claire!

Fred'n'Warren, strange the way the butterfly populations fluctuate.
"Throw what you like at us, we'll survive" - until, of course, they don't.

I wonder if there will still be 13 in the Partridge family after Friday 13th?

Mary said...

A lot of beautiful butterflies. I like that white moth...unusual. The Kestrel shots are wonderful...I wish they posed that well for me!