April Butterfly Survey

Now that April has arrived I've gone out into the 2km squares I have been allocated by STERF and chosen my exact transects for surveying. I have tried to get a range of habitats, both good and bad, to provide a true picture of the state of the butterfly population in the Touraine du Sud.

A Swallowtail Papilio machaon (Le Machaon) taking nectar from a
wild violet on the edge of the woods.

My survey sites are:

1. An area of unimproved grassland on the south facing slope of a limestone spur, surrounded by broadleaf woodland, once probably pasture, now mown perhaps once a year.
2. The steep grassy north facing slope of a limestone spur, being overtaken by conifers, junipers and other scrub, surrounded by mixed broadleaf and conifer woodland, once probably sheep pasture and now abandoned.
3. A rural track with improved pasture one side, broadacre crops the other.
4. A rural track through intensive broadacre cultivation.
5. A rural track through semi-improved pasture with a well vegetated ditch along one side.
6. An area of damp natural calcareous grassland, not grazed by domestic stock but may be occasionally mown, and wild boar forage extensively, surrounded by stands of broadleaf woodland, conifers and heath.
7. An area of damp natural calcareous grassland, not grazed by domestic stock, but wild boar forage extensively, surrounded by broadleaf woodland and beginning to revert to woodland.
8. An open ride through tall (2m+) heath scrub.
9. An area of flat open natural herb and flower rich calcareous grassland, mown periodically for hay.
10. A forest track along the edge of broadleaf woodland on one side and semi-improved haymeadow on the other.

A female Short-tailed Blue Everes argiades (L'Azuré du trèfle)
- she and her habitat (below) are in serious decline.

The species seen were (numbers refer to habitat list above): Dingy Skipper (8); Swallowtail (10); Brimstone (1, 5, 6, 7, 8, 9, 10); Small White (1, 2, 3, 5, 7, 8); Orange-tip (1, 2, 5, 7); Wood White (1); Violet Fritillary (1, 2, 5, 8, 10); Short-tailed Blue (9); Holly Blue (2); Small Heath (1, 9); Comma (8); Peacock (3, 5). Not only was the Brimstone seen at the most sites (7 out of the 10) it was also far and away the most frequently sighted in terms of individual butterflies, with 53 being recorded. Small Whites were encountered at 6 of the sites, but in fewer numbers than Violet Fritillaries overall (13 Small Whites and 18 Violet Fritillaries). High numbers of Brimstones is to be expected at this time of year, as they overwinter as adults. The average number of individual butterflies seen per transect was 10 and the average number of species 3.2. Each transect is 5m wide and as long as it takes to walk in 10 minutes whilst counting butterflies (in practice about 100 - 200m).

The lovely plum, ochres and shining white underside pattern
of a Violet Fritillary Clossiana dia (La Petite Violette).

Orange-tips have been recorded in exceptional numbers this year, but by the time I did my survey their numbers were dwindling somewhat (they are an early spring species), and perhaps my choice of habitats did not favour them. You tend to encounter them along ditches and damp patches with plentiful supplies of Cuckoo-pint, the host plant.

Habitat number 9 (those readers who travel between
Preuilly and Yzeures on the D104 may recognise it).

The poorest habitat was number 4, a track through broadacre crops (at the moment wheat). This transect produced no butterflies at all. The most productive habitat was number 1, a south facing calcareous grassland slope surrounded by woodland. Neither of these results is unexpected for this time of year. Intensively cultivated broadacre farms are generally poor butterfly habitat, whereas a nice warm south facing slope with some nearby woodland for protection is ideal for early spring.

Susan