Black Garden Survey 2021

 Black Garden Field, St Mary Bourne – 2020 Records – 22.02.21

Summary

Last year 4 rare species of butterfly were recorded on Black Garden Field, St Mary Bourne (the “Field”), the Small Blue, Marsh Fritillary, Grizzled Skipper and Small Heath butterflies.  Perhaps the most important find was a colony of about 30 adult Small Blues (numbers at the peak of their flight season).  The Small Blue has reasonably specific habitat requirements (see below) and it just so happens that those habitat requirements are presently being met at the south western end of the Field and at the south eastern end of St Peter’s churchyard.  

It is also possible that the Duke of Burgundy butterfly (Red List Endangered) might be present in the Field, as there are good quantities of its food plant, the Primrose, in the Field, albeit that none were recorded last year.  The Duke of Burgundy is “one of our rarest butterflies” (buglife.org.uk).

From an ecological point of view it is recommended that an ecological survey or surveys is undertaken before any changes are made to the Field, including any management changes.  The Hampshire & Isle of Wight Wildlife Trust may well carry out such a survey(s) free of charge. 

Introduction

Last year a total of 24 different species of butterflies were recorded on the Field out of a total of 62 resident and regularly breeding species (Fox, R et al, paragraph 2 page 3).

Of those species 2 are Vulnerable (Fox, R et al, pages 20 & 21) the Grizzled Skipper and the Marsh Fritillary, albeit that only one adult of each of these two species were recorded.

Of those species 2 are Near Threatened (Fox, R et al, pages 20 & 21) the Small Blue and the Small Heath, a colony of about 30 Small Blue adults was recorded and reasonably small numbers of Small Heaths were also recorded.

All other butterfly species recorded are of Least Concern.

For the record the Red List categories are as follows:

RE – Regionally Extinct
CR – Critically Endangered
EN – Endangered
VU – Vulnerable
NT – Near Threatened
LC – Least Concern

The Hampshire and Isle of Wight Butterfly Report – 2019 operates a slightly different system based on local abundance/rarity (“determined in accordance with South East England Conservation Strategy 2015-2-25 as adopted by the Hampshire & Isle of Wight” Butterfly Conservation branch, ref. page 13 of the 2019 report) and assigns the following butterfly species the Priority Statuses set out below:

Small Blue – High
Grizzled Skipper – High
Marsh Fritillary – Top
Small Heath – Low

Rare Species

Small Blue - Probably the most significant find in terms of a combination of number and rarity was the Small Blue colony that is located at the south western end of Black Garden Field (the “Field”) extending into the south eastern end of St Peter’s Church churchyard.  The Small Blue caterpillar foodplant is the Kidney Vetch and there were good numbers of this plant particularly in the south western end of the Field, but there were also reasonable numbers in the south eastern end of St Peter’s churchyard and in some other parts of the Field.  The Kidney Vetch is a pioneer species (ie it is one of those species that first colonises bare ground) and certainly the soil covering the south western end of the Field looks to be fairly thin and bare in places.  

The Small Blue butterfly is “much scarcer than its foodplant, flowering Kidney Vetch, … but a need for unusually sheltered conditions may be one answer” (Thomas, J & Lewington, R, 2010, page 114) which the above set out area of the Field /St Peter’s churchyard provides with its mixture of topography and vegetation.  The Small Blue is “our smallest butterfly” (Thomas, J & Lewington, R, 2010, page 114) and has the Latin name Cupido minimus.

Marsh Fritillary – The single Marsh Fritillary adult was also recorded in the south western end of the Field.

As this butterfly’s name suggests it is primarily found in damp areas, but “has colonised … over the past 75 years … unfertilised chalk and limestone downs” (Thomas, J & Lewington, R, 2010, page 225).  If the individual adult that was recorded flew in from nearby then some appropriate conservation work might encourage other adults to come into the Field and so start to breed there.  The Marsh Fritillary is “One of the UK’s most threatened butterflies” (ref. nationaltrust.org.uk/bideford-bay-and-hartland).

Grizzled Skipper - The single Grizzled Skipper adult was recorded in the north western end of the Field.  It is possible that there is a colony of Grizzled Skippers in the Field as they are quite difficult to see (given their small in size and moth like appearance) so more surveying work is needed to establish whether that is the case or if the recorded individual flew in from nearby.  If the latter was the case then again some appropriate conservation work might encourage other adults to come into the Field and thereby establish a colony.

Small Heath - The Small Heaths were mainly recorded in the northern part of the Field where it runs alongside the Egbury Road and in St Peter’s churchyard.  The Small Heaths that were recorded were scattered over a larger area and although the Red List categorises them as vulnerable, the Hampshire & Isle of Wight Butterfly Conservation branch only accords them a low priority status.

Full List of Butterfly Species Recorded

The only butterfly species whose numbers were counted in 2020 were the Small Blue, the Marsh Fritillary and the Grizzled Skipper.  Ideally a transect fixed route weekly walk would be made over the Field and St Peter’s churchyard during the butterfly flight season and the numbers of all butterfly species seen recorded, so that year on year comparisons could be made going forward not least to help inform any conservation work undertaken.

Hesperiidae (Skippers) x 3
Grizzled Skipper
Large Skipper
Small Skipper (and/or Essex Skipper, as they are not that easy to tell apart and the 2020 sightings/ photographs were not clear enough to enable them to be distinguished)

Pieridae (Whites & Yellows) x 5
Brimstone
Clouded Yellow
Large White
Orange Tip
Small White

Nymphalidae (Browns, Fritillaries & Aristocrats) x 12
Comma
Gatekeeper
Marbled White
Marsh Fritillary
Meadow Brown
Peacock
Red Admiral
Ringlet
Silver Washed Fritillary
Small Heath
Small Tortoiseshell
Speckled Wood

Lycaenidae (Coppers, Hairstreaks & Blues) x 4
Brown Argus
Common Blue
Holly Blue (mostly, but not exclusively, recorded in St Peter’s churchyard)
Small Blue

For the record the presence of the Small Blue colony, the Marsh Fritillary and the Grizzled Skipper in the Field has been reported both to the Hampshire & Isle of Wight Butterfly Conservation branch and the Living Record national database (the former confirming that they were not previously aware of the Small Blue colony) and there are photographs of the Small Blues, the Marsh Fritillary, the Grizzled Skipper and the Small Heaths in the Field and St Peter’s churchyard.

Plants

Good numbers of the following plants were also recorded in the Field and St Peter’s churchyard:

Broomrape(s)
Bloody Cranesbill (possibly)
Common Fleabane (in two distinct areas)
Common Spotted Orchid
Crested Dog’s Tail grass
Dark Mullein
Fox & Cubs and other Hawkbits
Goat’s Beard
Kidney Vetch
Knapweed(s)
Mallow(s)
Meadow Cranesbill
Ox Eye Daisy
Primrose
Pyramidal Orchid
Scabious(es)
Vetches/Trefoils
Wild Marjoram
Yellow Rattle

Management

The Field is presently being reasonably well managed from a conservation point of view in that it is generally being left alone and it seems that the grass in the main part of the Field is being cut quite late on after the wild flower seeds have dispersed.  It is not known whether the cut grass is being removed from the Field which would be ideal in order to prevent the build-up of nutrients and so allow the finer grasses and wild flowers to thrive and not be outcompeted by the coarser grasses (which do better in richer soils).  For the record areas that are managed for conservation, including for butterflies, increasingly use livestock such as cattle, ponies, goats and sheep to maintain and increase such areas’ biodiversity.

St Peter’s churchyard and in particular its eastern end is being sensitively managed as there is a profusion of wild flowers in this area and they are being allowed to flower and set seed.

Funding

According to butterfly-conservation.org Lottery and Landfill Communities Fund webpages there have recently been the following grants made:

Small Blue butterfly wildflower bank creation at St Julian’s Meadow, Greenwood Park, Chiswell Green – East England – 2019-2020;

Conserving the Duke of Burgundy and the Marsh Fritillary in Wiltshire – South West England – 2019-2020 and

Box Hill, Tadworth – Habitat Creation for Small Blue Butterfly – 2016.

Likewise, the Hampshire & Isle of Wight Wildlife Trust has recently purchased Deacon Hill, a 25 acre site just to the south east of Winchester that is “the area’s only stronghold of Duke of Burgundy butterflies” (bbc.co.uk, Wildlife trust buys Winchester land for butterflies webpage, 05.05.20).

References

Fox, R, Warren, MS, and Brereton TM (2010). A new Red List of British Butterflies, Species Status 12; 1-32. Joint Nature Conservation Committee, Peterborough. [Butterfly Conservation and Joint Nature Conservation Committee, No. 12, The Butterfly Red List for Great Britain]

Thomas J, and Lewington, R, The Butterflies of Britain & Ireland, British Wildlife Publishing, Gillingham, Dorset, 2010.