<meta name="description" content="Brown Hairstreak Habitat Advice from Butterfly Conservation "> BrownHstreak

Distribution The Brown Hairstreak (Thecla Betulae) is a scarce, local species. It has suffered a 25%-49% decline in numbers & range in Britain in the last 25 years. It does not occur in all the areas where there is apparently suitable habitat. In Berkshire, Buckinghamshire and Oxfordshire its main stronghold was thought to be the general area of Bernwood Forest but recent work has proved that this butterfly is present over a much wider area. Distribution as of September 2005 Woodland edges and a network of long hedgerows with a high density of blackthorn are essential for its survival. Colonies are usually small and centred on a particular wood, often on heavy soils. It also survives on roadsides. Butterfly Conservation will be pleased to confirm any suspected colonies. The easiest way to do this is through egg searches in suitable habitat in winter. Life Cycle The Brown Hairstreak is the last British butterfly to appear and does not emerge until about the middle of August although few may be seen earlier. It flies until October. As with many butterflies, the males emerge a week or so earlier than the females. General Habitat Requirements This butterfly occurs at low densities and a colony needs an extensive area with several kilometres of hedgerow, or sunny edges of woodland rides, with abundant Blackthorn. Males will congregate at a few 'master trees' . The females come in to mate, then disperse and lay their eggs over a wide area of hedgerow. Management Requirement Blackthorn bushes must be allowed to spread out from hedges, without regular trimming, as it is new low growth (often suckers) that is attractive to this butterfly. Ordinary cut hedges are suitable if they are cut on rotation.Because of their choice of low, new growth of Blackthorn on which to lay their eggs, at least four-fifths of them will be destroyed by any trimming operations. Hence, hedge cutting must be restricted to no more than two fifths of the total in any one year and preferably less. This is best done piecemeal, so that cut sections are not too long, and ideally in late July and August. Traditional layering is ideal as it is done on a rotational basis. Major tree felling should be avoided if possible as it is very difficult to identify 'master’ trees, but if unavoidable, the butterfly may transfer to another tree, provided there is a suitable one available. Deer Control Deer can completely prevent new Blackthorn growth from ground level to I.5m. After coppicing or clearing inside a woodland block it will probably be necessary to exclude deer. Boundaries and field hedges seem less affected. All sites have unique characteristics and current knowledge on management for this species is incomplete. Best advice may vary from site to site. It is advisable to try the several techniques described here on a series of small experimental plots and to monitor carefully, before commencing any large scale management. Please remember to consider the effects on a range of species before undertaking work to benefit a single species. If in doubt contact Butterfly Conservation for further advice. Searching for Eggs Brown Hairstreak egg on Blackthorn twig (10 times life size). A good way of monitoring the success of Brown Hairstreak colonies is to search for the eggs. They are laid singly on young growth of Blackthorn, usually at the base of a spine on a current year’s twig or below the junction of a new twig and the previous year’s growth. Most eggs are laid within I m of the ground on the outermost twigs of the bush or hedge. Searching for eggs from November to February is the best method of finding weak colonies. Identification This butterfly is the largest of the hairstreaks. but is very difficult to locate. Colonies are extremely diffuse and hard to find. The adult spends most of its time crawling high up among blackthorn and tall trees (often Ash), The golden-brown undersurface of the wings makes the adult easy to separate from other hairstreaks. Confusion occurs with the similarly coloured Vapourer moth, commonly seen spiralling about tree tops at the same time of year. Female Brown Hairstreaks are seen more often than males. They come low to lay eggs on Blackthorn (Prunus spinosa). very often on the outermost edge of the bushes, at heights below about a metre. The white eggs remain highly visible all winter. Searching low suckers on the southern edge of blackthorn-rich hedges and rides, from November to March, is often the best way to locate small colonies.
	· Underwings; golden brown, with pair of thin white Iines down each wing, halfway in. More orange outer border.
	· Upperwings: deep brown (opened to bask in weak sunshine). Male - faint yellow patch on forewings; Female: large orange patch on forewings
Monitoring The effect of any habitat change needs to be monitored. One way to assess the impact on butterflies is with a standardised recording walk or 'transect'. This allows comparison of populations from year to year. Butterfly Conservation will be pleased to advise on techniques and any alteration to management that monitoring results suggest. The Branch may be able to help with monitoring. Releases In order to judge habitat suitability and colony sustainability, wide consultation should take place before any release into the wild of butterflies. Releases should only be part of regional recovery strategies and are the last resort. Work to conserve and expand existing populations is much preferred (and easier). Further Advice This is one of a series of advice leaflets prepared by the Upper Thames Branch of Butterfly Conservation. Please contact us for further information, or for help with species identification and monitoring at: