If you regularly walk through Yeoman’s Field, you will have noticed our wardens and work party volunteers have been cutting back areas of blackthorn and bramble. So, what are we up to?...
Two years ago, a brown hairstreak butterfly was seen near our Visitor Centre. Hairstreaks are generally an elusive family of butterflies, prone to hanging around the tops of their preferred species of tree. Brown hairstreaks are also brown and orange in colour, and unless you knew what you were looking for, they can easily be overlooked as a gatekeeper or meadow brown, which are plentiful across our reserves. Not surprisingly then, that we have no records at this site, certainly not in the last decade. This sighting started us thinking – maybe they had been here for a while and just not been seen, identified or recorded. So that winter our work party volunteers and wardens undertook the daunting task of trying to find brown hairstreak eggs. The eggs, as you can imagine, are tiny, about the size of a pinhead. They are laid singly at the base of branching blackthorn twigs. None were found around the Visitor Centre, but amazingly, a couple were found in Yeomans Field.
Brown hairstreak - Patrick Cashman (rspb-images.com)
Now as you enter this field there is a small stand of elms. Elm just happens to be the tree which the brown hairstreaks cousin, the white-letter hairstreak, is solely reliant on for its lifecycle. Like brown hairstreaks, this is a species not often seen. Unless of course you are looking up! Into elm trees! So again, it is no surprise that this is not a butterfly recorded on our reserve. So, on a hunch, I spent several lunchtimes last July standing in Yeomans Field staring up into these elms with my binoculars. Sure enough, it was not long before I was rewarded with a number of brief, but good enough sightings, to positively identify white-letter hairstreaks moving around the canopy.
A month later and my lunchtimes were spent walking up and down the blackthorn hedges. This was unfortunately less fruitful, but I did manage to get one very good view of a male brown hairstreak as it soaked up the sunshine. However, just before Christmas our wardens and work party volunteers again surveyed the blackthorn for brown-hairstreak eggs, concentrating on Yeomans Field and this time found four eggs. Not many you may think but it is enough.
Brown Hairstreak egg - Luke Parham
Both these vulnerable species, white-letter and brown hairstreak, appear to be resident and breeding on the site.
Which brings us to the work we are doing in Yeomans. Brown hairstreaks like fresh growth and as advised by Butterfly Conservation we are cutting sections of blackthorn on a 5 year rotation to encourage different ages of growth which we hope will be attractive to the egg-laying females.
Meanwhile we have been clearing the bramble around the elms, so they don’t get choked and have a chance to sucker. The caterpillars of white-letter hairstreaks have been found to survive on elm suckers even when main trees have died.
Room for elms to breath! - Luke Parham
To add to this the work party has also reinstated the path than runs through the blackthorn stand and started to open up the pond.
Work party hard at work - Luke Parham
This summer we are planning on completing regular butterfly surveys in Yeomans Field - if you would like to help with these surveys please do get in touch by emailing us pagham.harbour@rspb.org.uk
And if you're wondering about the name Yeoman's Field, a yeoman was the old English name for someone who owned and cultivated land.