Butterfly Survey 1999

Visits made when temperature was 17 degrees (cloudy) / 15 degrees (sunny) wind speed not above 5 between 10.45 and 15.45.

Survey route follows south edge of lower Leach Fields (Sections 1&2) / up centre of lower fields (Sections 3&4) / through to upper field (Sections 5&6) / across upper field (Section 7) / across Parish Council Moffats Open Space (Section 8) / down West Boundary Path (Sections 9&10) / along Centre Path (Section 11) / along South Path to end of plantation for Battersby & Parsonage (Section 12) / back along path to path across Brazier plantation (Section 13) / across Little Rye (Section 14) & finally along public footpath to Brook House (Section 15). This route takes approximately 1 hour to complete and was visited approximately once a week.

This is the last year that results from this survey are sent to the National Millennium Butterfly Atlas Survey via the Hertfordshire County Recorder. We have now recorded 24 species since we began recording in 1990 and this year 19 were seen. The five species not seen were Dingy Skipper, Painted Lady, Small Copper, Wall Brown and White Letter Hairstreak. A new species, Ringlet, was recorded for the first time.

Butterfly images 1999
Butterfly Survey Details 1999

April had a reasonable sunshine levels with normal wind speeds; May continued its recent trend of being sunny with a particularly warm week (22°C) towards the end of the month; June maintained average temperatures but sunshine levels were very mixed and the first part of July was very cloudy followed by a good spell of high temperatures (30°C) and sunshine albeit often hazy and humid. This continued in August. However September quickly deteriorated into cool and windy weather and very few field visits were possible.

Over the ten years of the survey weather patterns have fluctuated as might be expected but it seems that there has been an increase in average wind speeds, which does affect the number of butterflies flying, and in cloud cover which also affects population levels. Very high sunshine years are offset by years with poor levels but average temperatures have risen although without good sunshine this is more significant for habitat particularly when associated with longer periods of drought which has also been the case over the period. Sighting levels are very much related to weather patterns but overall population levels are also affected by habitat changes whether they be man-made or “natural”.

As habitat changes occur in the various sections this is reflected in sightings but this is a normal occurrence and one has to remember that 99% of the UK habitat is man-made and in many cases man's activities have made it possible for certain species to thrive, eg the chalk downs where the introduction of rabbits by the Romans created the conditions for butterflies like the Blue species to become established. Most woodland species need sunny areas in which to bask, mate etc in their adult stage, originally created by natural tree cycles, forest fires etc and now in today's managed woodland by coppicing. However it is also important to have as good a mixture as possible of woodland plants including the taller less “popular” ones such as burdock, thistles and nettles to grow throughout the summer in the cleared areas and along paths. Although it isn't popular with walkers to have nettles lining paths if we are to maintain butterfly populations in the wood we have to accept their habitat needs, likewise it is important to maintain a certain level of ragwort in the fields as this is an important basking and food plant for several of the field butterflies and moths. The leaving of wide uncut margins in the fields is a compromise between the needs of insects and that of hay for sheep.

The planting of buckthorn in Leach Fields has seen increased numbers of Brimstone now recorded not just in the fields but also in the south-west corner of the wood but this has to be offset by the decline of the Small Heath which is County-wide and for which it is very difficult to account. Our two most populous butterflies over the decade are the Meadow Brown and Gatekeeper; the other species which flies in great numbers, the Skippers, are much more affected by poor springs but populations remain good particularly the Essex Skipper, although it is noticeable that in Little Rye where the grass is not cut numbers have fallen steadily. Other field butterfly populations have been maintained during the decade with all being affected by cold, wet springs but generally picking up in good years. It is pleasing to report that in the last year of the decade the Ringlet has finally been recorded: we have been looking for this for years as the habitat in Leach Fields is right for this slow-moving, dark butterfly with its distinctive five circle markings.

Of the mainly woodland butterflies, the Speckled Wood continues to flourish and has now spread throughout the whole survey area. Regrettably the White Letter Hairstreak may prove to be an occasional visitor; the dubious health of their food plant, the elm tree, is no doubt the real root of the problem. We have yet to record any Purple Hairstreaks although they have been seen near Gobions Lake but as what one is normally looking for is a small silvery insect at the top of oak trees this does not surprise me!

Preliminary results from Hertfordshire/Middlesex Butterfly Conservation show the greatest number of species (ie great biodiversity) in the chalk hills in the north-west of Hertfordshire around Tring, west of Hitchin and at Therfield Heath. Good biodiversity is also shown in the wooded parts of Hertfordshire between Hertford and Stevenage, Watford and Borehamwood and at Hampstead Heath. Although specie numbers have decreased in some areas in others, such as north of Hertford, they have increased. Most encouragingly parts of Greater London and Middlesex have also seen an increase in numbers since Brian Sawford's survey during the 1980's which may be due to more enlightened management of parks and open spaces in particular the non-cutting of grass during the summer. Hopefully the full results will be available some time this year.

The Trust is to continue monitoring transects. Thanks again to the recorders for their regular and consistent help.

Linda Jonas March 9, 2000

Patron: The Marchioness of Salisbury
Trustees: Iain Aitken, Jerry Golland, Michael Jonas and Bernard Spatz

Other sections of the Gobions Report 1999
Annual Report 1999
Butterfly Survey 1999
Butterfly Survey Details 1999
Ecological Survey
Bird Survey 1999

Annual Report 1998

Butterflies of Gobions Woodland
Butterflies 1-5
Butterflies 6-10
Butterflies 11-15
Butterflies 16-19
Butterflies not sighted during 1999 survey

Butterflies seen in 1998

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