US social scientist Kenneth Boulding : ‘If you believe exponential growth can go on in a finite world, you are either a madman or an economist’.

Showing posts with label White-letter Hairstreak. Show all posts
Showing posts with label White-letter Hairstreak. Show all posts

Tuesday, 20 July 2010

20/7/10: Another new White-letter Hairstreak colony in Bexley

Following on from my White-letter Hairstreak butterfly find at Crayford Marshes (see 2/7/10 posting), late this afternoon I checked Barnehurst Golf Course for the presence of White-letter Hairstreak for the second time in a fortnight.

I had had a possible 4 sightings on 6th July, 3 along the fairly substantial strip of English Elm along the western margin of the site bordering Manor Way, and 1 at the eastern end parallel to Perry St, where there is another reasonable amount of Elm. All were briefly in flight and I could not see where they settled to get a proper view and confirm presence.

Today, besides a possible sighting at the Perry Street end, I obtained a definite identification by the Old Manor Way entrance at the west end of the site (TQ 506 760). I had been pondering the dearth of suitable nectar sources in the immediate area when I saw a small brown butterfly land on a cluster of the few Bramble flowers not yet setting fruit, just as I was about to exit the Golf Course and head for home. I swung my binoculars onto it just in case it wasn't another Gatekeeper, and because I'd seen a possible White-letter Hairstreak on an Elm 'bush' here two weeks ago. And lo, and behold, a W-LHS it was! Cue a bit of fist-pumping, but not too obviously in case any passers-by thought I was some kind of nutter ..... The insect was about 8' from me and only a few yards from gardens and houses on either side. The time was 18.17 and it was a warm, sunny afternoon with a slight breeze. The area where it was feeding was still getting some sun from the west at this time.


A White-letter Hairstreak was seen feeding on Bramble flowers here at the 'stub end' of Old Manor Way, by the entrance to Barnehurst Golf course, early this evening. Dead, ivy-clad Elm to the left, live Elm centre, Pedunculate Oak right. Swathe of Bramble, Stinging Nettle and Mugwort in the foreground.

A bit of subtle management to improve W-LHS habitat would probably be useful here. The Elm is reaching a decent height before succumbing, but there is relatively little coming through in the way of mid-height (or even small) suckers. This is because a considerable number of dead Elm have been left in situ and are covered in Ivy, shading and swamping out new growth. Several medium-sized Sycamores are taking up space that Elm could colonise. And in one area a Russian Vine from a neighbouring garden is covering an increasingly large area within the Elm zone whilst a dense swathe of bordering nettles is hindering any Elm colonisation along the margins of its present extent.

At any rate, the fact that I've trebled the apparently 'known' number of W-LHS sites in the Borough in 2 weeks rather supports other people's theories that the species is under-recorded - it's not the sort of thing that one is necessarily going to find on the basis of a few cursory glances up at a bunch of Elm trees. Indeed the LNHS butterfly recorder tells me it has already shown a very large increase in records between the 1980s and 1990s - the second-highest of any butterfly species in London - which suggests better recording rather than a massive population increase and spread.

Elsewhere on the Golf Course today, Essex Skipper, Gatekeeper, Meadow Brown, Holly Blue, Small Copper and Red Admiral were seen. The usefulness of the oft-maligned Common Ragwort as a nectar source for several of these butterflies, at a time when not much else is available in such grassland, was especially evident.

Friday, 2 July 2010

2/7/10: New White-letter Hairstreak colony in Bexley

The LNHS Horsenden Hill meeting, which was the first time I'd seen White-letter Hairstreaks, was a useful event for getting my 'eye in' and was absolutely instrumental in enabling me to find the species along Moat Lane on Crayford Marshes today. I was also spurred on by Tristan Bantock having said he also thought there was a good chance of it being there when we were making our way along the lane towards Slade Green aftera bug-hunt earlier in June.

Moat Lane, Crayford Marshes, on a sunny evening back on the 23rd April 2010. The substantial English Elm 'hedge' where the White-letter Hairstreaks were found is on the left (south) side, here catching the evening sun from the west.

The lane has longish stretches of English Elm 'monoculture' to about 18-20' tall along the south side, and a few rather smaller ones on the north side. Horses are pastured on the rough grazing adjacent to the hedge. I saw between 7 and 9 likely different individuals, two of which I got side-on good binocular views of and so can be absolutely certain of the ID. They appeared to only be using the (south side) Elm some way along the lane at present (around TQ 530 767), and not that near the Slade Green station end or opposite the moat of Howbury Grange.

The weather was hot and sunny, with some blustery breezes and the odd dark cloud blotting out the sun for short periods. The observations were made between 11.40 a.m. to around 13.30.

The White-letter Hairstreak is a UK and London Borough of Bexley Council BAP priority species, and the Council's website says the only place it occurs in the Borough is in a wood at Foot's Cray Meadows.

Other species seen along the lane today were:

Probable Holly Blue
Common Blue
Large Skipper
Small Skipper
Small White
Meadow Brown
Comma

and a couple of female Broad-bodied Chasers and Darter species.

There were 4 Swallows (probably fledglings) sitting on the barbed wire fence of the field around the moat, and a few Swifts overhead.

Coming hard on the heels of the W-LHS find, a little further along the lane towards the River Darent were 2 or 3 clumps of Crown Vetch, my second find of it in the Borough - the other also having been on the Marshes, in that case away to the west near Crossness.

Out by the river were a Small Heath, 2 Common Blues, a Kestrel and Tufted Vetch.

Saturday, 26 June 2010

26/6/10: Horsenden Hill - White-letter Hairstreak

A 'holding' catch-up posting so that some more recent ones will make sense ....

LNHS meeting, Horsenden Hill, Perivale, for White-letter Hairstreak butterflies (Satyrium w-album), which were duly observed in their favoured Elm tree habitat. This is was the first time I'd seen the species, and was the main reason for attending this event.