Brown Hairstreak in the Arnside and Silverdale AONB

Local naturalists and visitors to North Lancashire will be aware that the Brown Hairstreak butterfly has been recorded in and near to Coldwell Parrock and Gait Barrows NNR over recent years. This has generated great interest and discussion. Visitors are sometimes rewarded with first personal sightings of adult Brown Hairstreaks and other life-stages including egg and caterpillar stages.

A little history?

The first AONB Brown Hairstreak sighting in the modern era was made by Michael Smith at Coldwell Parrock in 2011. Adult and egg sighting quickly followed at Gait Barrows.  A search of historic butterfly records and literature revealed that the previous recorded sightings of this species in this area were in the 1920s and 1930s ‘in the Silverdale area and Grange over Sands’, (Collingwood and Lowther 1932). Records at that time indicated the species being ‘present’ rather than giving a numerical value showing abundance. Regular Brown Hairstreak egg searches over recent years have been in excess of 180 eggs annually providing clear evidence of breeding success. Adult too have been recorded in reasonable numbers.

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The AONB has a strong history of butterfly and moth recording by experienced naturalists. The likelihood of this species being overlooked in the area by recorders in the intervening years between the 1930s and 2011 is considered improbable. The species can be assumed to have been extinct until recently.

How did the Brown Hairstreak arrive in recent years?

The nearest colony is located 150 miles away in the Lincolnshire Lime-Wolds east of Lincoln. This is considered much too far distant from which the species could colonise the Silverdale area naturally.

It is now known with certainty that a local naturalist has bred the species in his home setting over successive years – 7 years at least. The resulting adults were subsequently released at a location not very distant from Coldwell Parrock and Gait Barrows. 

Local interest

There has been great interest, indeed excitement, despite the fact this species has not arrived naturally. Many people have enjoyed the challenge and the prospect of observing and learning more about this interesting species through direct observation and discussion. This includes: 

• life cycle (opportunities to view egg, larvae and adult stages)
• understanding habitat requirements – blackthorn management, use of blackthorn and ash trees at adult stage (‘assembly’ trees)
• observing behaviours – mating, egg laying, hibernation, larval emergence and feeding, adult nectaring and their breeding preferences
• gaining knowledge and experience of other arboreal species, such as Purple Hairstreak on oaks

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Butterfly breeding in the UK

Please note:

It must be stated that conservation organisations – Butterfly Conservation, Lancashire Wildlife Trust and Natural England, don’t support unofficial butterfly releases intended for large scale introductions. There are strict criteria that apply to gain permissions and acceptance of organised butterfly releases.

Small scale insect breeding is not uncommon in the UK. This is sometimes carried out by individuals for perhaps ‘well-intentioned’ reasons to further their knowledge of life-cycles or for identification purposes. They release butterflies and moths into the wild from captivity, usually as adults or on occasion late caterpillar instar stages. The problem is that casual releases, even of widespread species, can confuse existing planned conservation effort and the recording of a species’ natural range and population trends. Butterfly Conservation’s policy states that ‘all large-scale releases should be properly planned, authorised by all parties concerned and undertaken through environmental organisations that have a record of success’.  In the North West examples of such schemes include the excellent Lancashire Wildlife Trust Large Heath introduction to their Heysham LWT reserve. Another is Natural England’s sanctioned Marsh Fritillary reintroduction project in North Cumbria. This project has been so well organised that Marsh Fritillary colonies are now breeding successfully in 20+ former sites following habitat restoration at landscape level. The species was saved from extinction at the 23.59^th hour.

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In Conclusion

It’s been an exciting Brown Hairstreak learning journey for many naturalists over recent years at Coldwell Parrock and Gait Barrows. Egg counts and other life-stage sightings over successive recent years have provided clear evidence of breeding success at both sites. However unofficial introductions have a generally poor record of success across the UK. Most species have exacting demands of required habitat conditions necessary to sustain a colony over a continuous period of years. The Brown Hairstreak in the AONB may experience this difficulty? Only time will tell in the coming years…

References and further information

• The Lake Counties – W.G. Collingwood first published 1902, revised 1932
• The Butterflies of the British Isles Richard South, new Edition 1921
• NBN Atlas 2017 record Heathwaite Arnside dated 1920
• An early summary of the Cumbria Marsh Fritillary reintroduction which has gone on to further enormous success
• An excellent YouTube video on the Brown Hairstreak lifecycle: