Branch Newsletter

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NEWSLETTER No. 9 - Summer 1983

WEST MIDLANDS BRANCH, BUTTERFLY CONSERVATION

After lunch our second speaker, Martin Warren, took the floor. He briefly ran over the extinctions in Britain and then moved on to a look at the Wildlife and Countryside Act.

The species given legal protection under the Act are the Large Blue, Chequered Skipper, the Heath Fritillary and the Swallowtail, although the reasons for the late inclusion of the last of these are less than clear. The Act contains a far-reaching clause making it illegal to disturb, have or kill the butterfly or to disturb its habitat. As photography could come within this definition it does not seem that enforcement will be very easy.

A study of endangered species in Europe by John Heath was then examined and it was noted that the Large Blue was included. This came as something of a surprise as the extinction of our Large Blue was always to some extent played down by the reported abundance of the same species in Europe, but this is not the case. Species listed as vulnerable in Britain are the Swallowtail, Large Tortoiseshell, High Brown Fritillary, Heath Fritillary, Adonis Blue, Silver Spotted Skipper and the Large Heath (in England). The Large Tortoiseshell may already be down to immigrant status (see article in this newsletter).

A look at distribution maps then appeared to confirm a definite westward drift. To arrest this decline it would be necessary at least to slow down the loss of habitat. NCC figures make horrifying reading and show the loss of 30-50% of deciduous woodland since 1947, 21% of chalk downland since 1960, 25% of hedgerow length between 1946 and 1974 and similar rates of disappearance for heathland, bogs and all other habitat types. In this context, habitat conservation becomes even more important. Reserves and unspoiled areas must be conserved to provide habitats and to combat fragmentation of population caused by the disappearance of what are intermediate habitats.

Once habitats are safeguarded, the contentious question of re-introduction can be looked at. There are many arguments for and against which were not fully explored, but it was stressed that any introduction or re-introduction can only be of value when very carefully researched so that harmful effects could be avoided. (The Branch would be interested in having member's views on this subject).

A study of a woodland habitat undertaken by Martin was then followed through. Bearing in mind that a good woodland habitat could have 30-40 species many woods are sadly deficient. The answer to the suitability lies not only in the type of woodlands but in the rides. All species need rides for nectar sources and in many cases for foodplants as well. Even species such as the White Admiral and Silver-washed Fritillary which very often lay eggs within the wood need sufficient rides for nectar plants.

Whether a ride is suitable generally depends on the amounts of sunlight available. An interesting set of slides was shown giving populations within individual rides at different times showing a definite correlation between sunlight and butterfly populations for several species. The amount of sunlight reaching a rides is affected by its width, whether it is north/south facing, and the height of trees on either side. The last factor of course alters with time, making a rotation of suitable rides the only way to maintain suitability. Historically, coppiced woods up to the 18th century were ideal for this. It was also pointed out that mechanical cutting of scrub in rides does not do as much damage as might be supposed. In one example in Monks Wood, of fifty Wood White pupa marked prior to cutting by this method, only one was killed.

An overview of other types of habitat conservation was then undertaken. It was interesting to note that although mowing can be used to maintain grass height at the same level as grazing, it did not encourage the growth of some plants. One of the major problems facing our conservation efforts is the lack of knowledge of the many inter-related factors which affect suitability for sensitive species such as Adonis Blue.

A look was then taken at the Large Copper. The first attempt at re-introduction was as long ago as 1909. There have been attempts in Bire which lasted from 1913 until 1936 and from 1942 until 1955 and another in Norfolk which lasted for two years. The 1927 attempt at Woodwalton Fen still survives only with the intervention of support breeding, as those of us who visited the reserve two years ago saw. Now that the fen is surrounded by agricultural land which has shrunk as it was drained, the remaining Fen is 15 feet above the surrounding area and is only kept wet by pumping. The area is probably too small to ever support a fully self-sufficient colony.

The Heath Fritillary was the next species examined. This butterfly has always been local but has now disappeared from East Anglia and the Midlands. The remaining locations which have declined in number are in Kent and the West Country. The Kent sites are in recently coppiced woodland where cow-wheat is common, whereas those in the West Country are more open, such as an abandoned hay meadow and some abandoned strawberry fields. Several of the West Country sites have been lost and others are under threat from conifer plantations. Two sites are now reserves and the Devon Trust is negotiating for a small site. There are serious management problems in keeping out bracken. The Kent sites in woodland recently acquired by the RSPB and the NCC are fragmented and in partially coniferised woodland. The cyclical coppicing is threatened by the fact that cheap timber imports are making it uneconomic.

The Adonis Blue is another vulnerable species which is declining throughout its range. Present sites are all south facing with short turf. Dorset has lost several sites where the foodplant still exists but where grass has grown higher than about 4cm which seems to be the limit for this species. The reason for this is not clear. It is known that temperature can be affected by as much as 8 degrees Fahrenheit by the differing grass lengths and this may have an effect on egg laying. It is also known that the pupae are attended by ants but again, the significance of this is not understood.

The last species considered was the Black Hairstreak. It is now know that this species does not move around within a wood, but a colony will stay in one place for many years. As stands of blackthorn dies back at 50-70 years it is therefore essential to have new stands available for the colony to transfer to.

Roger Smith then closed the proceedings with a vote of thanks to both speakers for a day of interest which had covered such a wide area.

The West Midlands Branch are particularly grateful to Roger Smith for organising such a successful day, which was greatly enjoyed by all those taking part.