Success stories!
Our first Adonis Blues! On 31st. May three of these beautiful butterflies were seen on the reserve for the first time. This is cause for celebration as for some years now we have been trying to prepare the ground, as it were, in the hope of attracting them. Over the last few winters we have seeded and plug-planted the butterfly bank on Football Field with, amongst other chalk grassland plants, Kidney Vetch and Horseshoe Vetch; the former being the larval food plant of the Small Blue, and the latter, that of the Adonis Blue. The Small Blue story has been an ongoing success in its own right with good numbers having been seen over the last couple of years across the reserve particularly on and around our two butterfly banks - but the Adonis Blue is known to be a more difficult butterfly to attract. It favours south-facing, short-turfed slopes particularly on chalk, which we have made efforts to provide; but this species is known to be a stay-at -home type, and to not venture far from its home colonies (which sadly, nowadays, are few and far between). I had seen them before at Beacon Hill near Tidworth, and on the old railway path alongside Boscombe Down airfield, and they are something to behold; if the light is right, the blue of their upper wing surfaces flashes out like a bright light, over some distance. This is not always apparent, especially on an overcast day and particularly as the butterflies age, as the colour and brightness are an effect of light reflection (or is it refraction?!) on tiny wing-scales, which gradually get worn off over time - the base colour of the wings being brown, like those of the female.
Male Adonis Blue on one of our butterfly banks by Roy Williams
So, all in all, great to see them here. Chalkhill Blue next? Its requirements are similar, its larval food plant the same - here's hoping.
Not a first for the reserve, this next one, but still a good sighting - Marsh Fritillary, also in Football Field, on 31st. March again. Once again it's not a great traveller, it tends to live in discrete colonies, which doesn't help its chances, and it's in serious decline ( Species in isolated colonies go extinct more easily - hence the idea of wildlife corridors to join these areas up). It was known to be present on the Porton Ranges and last year was seen on Winterbourne Downs adjacent to the Portway and the railway line, a short flutter away! Its caterpillars feed on Devils Bit Scabious and Small Scabious which are now well established on the reserve, another testament to the hard and wintry work of our conservation volunteers and their chilly plug-planters hands!
Marsh Fritillary on RSPB Winterbourne Downs by Patrick Cashman
Football Field is some distance from this area so it's a good sign to see this one a bit further afield - hopefully this is the first sign of the species spreading across the reserve.
Will keep you informed of any more success stories - let's hope there will be plenty more!
Roy Williams
RSPB Volunteer Warden