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Much of our knowledge of the wildlife of Marshalls Heath comes from casual observations from ordinary people. We are pleased to receive reports of what has been seen from anyone at any time; the minimum requirements for a record are:
plus of course your name. Send these details to John Murray at: firstname.lastname@example.org
In addition, many records come from traps and standardized methods of recording. One of the simplest of these is the transect method, used at Marshalls Heath for recording butterflies, and many birds have been identified on the basis of their call alone.
Many shy birds, plus others difficult to identify on sight or from the brief glimpse one normally gets, can be identified from their distinctive song. The best time to record birds in this way is during the dawn chorus, particularly in the spring. There is an excellent Collins field guide entitled "Bird Songs & Calls of Britain and Northern Europe, which includes two CDs containing all the major songs and calls of the common birds, and the RSPB also have similar recordings for sale.
Many species of plant, animal and insect are tricky for the amateur to identify, so any kind of photograph, however bad, can often make the difference between a positive identification and a "possible". The advent of digital cameras means that large numbers of photographs can be taken at no additional cost, and the results can be transmitted instantaneously to experts for identification.
These cause no harm to the mammals when caught, and are very useful for survey work. The method has not yet been tried at Marshalls Heath, any takers?
Transects should only be carried out by experienced observers who can recognise virtually all butterfly species on the wing. The method consists in walking the same route at least once a week between 1st April and 29th September under standard meteorological conditions of temperature, wind and sunshine, and noting the numbers of each species of butterfly seen within 5 metres of the observer. This method gives information on the variation in butterfly numbers within the season, and from year to year. It is the main method by which declines in species can be quantified, and as such is extremely important.
The butterfly transect at Marshalls Heath was first walked in 1988, but good coverage was not obtained until the early 1990s. At present it is normally walked by John Murray, Trevor Chapman and Michael Healy. The results are published each year by Butterfly Conservation, in their Annual Report.
Heath light trap
This consists of an ultraviolet light suspended over a cone that narrows into a box in which empty egg cartons are placed (see picture on right). Some of the moths attracted to the light fall into the box. They could fly out again, and doubtless many do, but most think that the bright light means that daylight has returned, so their instinct is to crawl into the shadow of the egg cartons where they are found in the morning. The moths are not harmed, and can be released after identification.
The trap is normally set up at ground level on the border of Marshalls Heath near the houses north of the woodland. It is normally operated by John Murray, but species difficult to identify, particularly the smaller microlepidoptera, have been identified at various times by Mark Sterling, Phil Sterling, Colin Plant (Hertfordshire recorder for moths and leader of the Hertfordshire Moth Group), Raymond Uffen, Adrian Riley, John Langmaid, David Aggasiz, Klaus Sattler, Jim Reid, Norman Hall, Andy Beaumont, Steve Nash and Colin Hart. Occasionally, more powerful traps are operated on the Heath itself, sometimes several at a time for special "moth evenings".
Large numbers of other insects and invertebrates are often caught in the moth trap, the largest probably being the huge day-flying Southern Hawker dragonfly (Aeshna cyanea). Others include wasps, earthworms, slugs, caterpillars, a male glow-worm and many other types of insect.
Moths attracted to house lights
Moths which fly into houses at Marshalls Heath, or are attracted to porch lights are also noted. Many species attracted to the house lights have not turned up in the trap.
Another method of attracting moths is to mix treacle, rum, and various other delicious ingredients (recipes vary from one enthusiast to another) and spread the mixture in a perpendicular stripe on trees and fences. The method seems most successfuil on calm, warm nights. The method attracts some species which do not seem to be attracted to light, so the two methods are complementary.
The larvae of some micro-moths and other insects make characteristic "mines" or blotches in leaves, which can be assigned to one particular species by their shape, and the species of plant used. The method can be extremely effective: Mark Sterling visited Marshall's Heath on 17th September 1994, and in an hour or two, 32 different species were identified, 29 of which had not been recorded here before.
The photograph on the left shows a leaf mine made by the caterpillar of the tiny moth Stigmella aurella, (Marshalls Heath, February 2002)
This was invented by an entomologist called Malaise, who was always perplexed to find that after a day spent searching for insects, he always found much more interesting insects in his tent when he got back in the evening. The design is essentially a modified tent, in which the insects are caught and try to escape upwards towards the daylight. This is the best trap for attracting bees, wasps and flies. It has not yet been tried on the Heath, but there are plans to do so this year.
Where do the records go?
Records of wildlife have the greatest value if they are distributed to all who need to use them. Most records go to the various county recorders of the Hertfordshire Natural History Society, and also to the Hertfordshire Biological Records Centre (HBRC), who keep county records for all of Hertfordshire. From time to time, records of newly discovered species here are also sent to the Herts and Middx Wildlife Trust.
The butterfly records also go to Butterfly Conservation Hertfordshire and Middlesex branch, who in turn pass them on to the national organisation. They helped to create the Millennium Atlas of Butterflies of Britain and Ireland, published in 2001. The butterfly transect data also goes to Butterfly Conservation, where it has been particularly valuable to the Department for Environment, Food & Rural Affairs (DEFRA), who have a long term project with Butterfly Conservation to study the effect of Agro-environment schemes on butterfly numbers.
There are several local splinter groups for particular taxa, more or less associated with the HNHS. Moth records also go to the Hertfordshire Moth Group, who are producing a new book on the moths of Hertfordshire, and particularly interesting finds are reported to John Langmaid of the British Entomological and Natural History Society. The plant observations go to Trevor James, who is compiling a new Flora of Hertfordshire, and dragonfly records to Christine Shepperson of the Hertfordshire Dragonfly Group. Hopefully much of this data will be widely available eventually through the National Biodiversity Network.
Updated 27 Feb 2003