Woodland species

[eccles]

I live near Willsbridge valley, an 8 hectare Avon Wildlife Trust site comprising mainly of mixed deciduous woodland that sits astride a brook. There are a few open glade areas with bramble, also a small meadow. Last year for the first time at the site I saw a single and rather tatty male silver washed fritillary and assumed it was a vagrant. Then two days ago I saw another, followed yesterday by a single white admiral. The SWF was there again today, at least I think it was the same one.
I assume again that these are vagrants, although where from I have no idea, but this leads me to ask the question: what sort of size of woodland is necessary to support colonies of these two species? Is 8 hectares big enough?
For the SWF, I saw its foodplant, common dog violet, flowering earlier this year in several places and there are several oaks of different ages which are needed for larvae to overwinter. For the WA, I only know of one place on the site where there is its foodplant, honeysuckle, but it's quite a large plant.
Currently there are speckled wood, gatekeeper, meadow brown, ringlet, holly blue, red admiral, comma, peacock, brimstone, orange tip, large, small and green veined whites regularly breeding there.
Any comments appreciated.

[ChrisJB]

Dear Eccles,

I keep reading that both these species are 'doing well' and spreading to former areas where they were once found, as well as new areas. There was even a Silver Washed Fritillary turned up in Rochdale (Lancs) not far from me, last summer.

Looking at distribution maps in my books, both species seem to be present in Avon and off the top of my head, eight hectares would be big enough to support populations.

I just wish their advance north was a little swifter!

Regards, Chris

[eccles]

Thanks for that Chris. On that basis then the site may well be colonised by SWF provided we get females there. They aren't perhaps as mobile as the males though. If I could figure out where these males are coming from I might be able to guess the likelihood of females following depending on if sufficient woodland is between where they're coming from and where they're going to.
I was asked by a full timer at the site about planting foodplants a while ago, so I'm now going to lean on her to plant some more honeysuckle. It's good nectaring for moths like elephant hawks anyway even if we don't get the white admirals.