Slow Start to the Big Butterfly Count

The annual citizen science event the Big Butterfly Count has come to the end of its first week and people around the country are reporting concerns about fewer butterflies, but not just butterflies, it appears there are fewer bees and other flying insects.

Whether this is a real phenomenon or just misjudging the seasonal peaks and troughs remains to be seen as the summer progresses. The exceptionally wet April may have affected numbers as over-wintering larvae and pupae might have suffered in the waterlogged conditions, especially the species that hibernate underground and at the base of rank grasses.

In the town’s uncut grassland areas such as The Knapp and Knowle there are plenty of Ringlets with their chocolate brown wings fluttering about in a rather chaotic way. This raises the contentious issue of grass cutting.

People are delighted to see butterflies and often plant particular flowers in their gardens to attract and feed these flying jewels. The problem is that their larvae (caterpillars) do not feed on nectar but eat greenery, as people who grow cabbages will tell you. Much is made of Red Admirals and Small Tortoiseshells needing nettles, but the food plants for many of our butterflies are the rank grasses that you find in meadows and pastures.

The decline of butterfly species across the countryside is well documented as farming practice changes introduced to produce more food for humans have reduced the feeding opportunities for many insects. If we want to see butterflies in our towns and gardens then we need to give them all the help we can. No mow May is a good start for flowers and nectar feeding adult insects, but many butterflies need the long grass to be around much longer to complete their life cycles.

The cemetery is an interesting case. Last year two areas of the original cemetery were left uncut and the long grass persisted into late autumn. A fifteen minute butterfly count in the northern area on 20^th July recorded 42 butterflies and moths representing 6 species. Half were the long grass feeders Meadow Brown and Gatekeeper performing courtship dances and dipping down to lay eggs.

This year the northern of the two sections has been cut regularly and is kept as short grass. A fifteen minute count in this section on 14^th July this year recorded just one butterfly, a Meadow Brown. This is a week earlier but a count on the same day in the still uncut southern section recorded 24 butterflies from 4 species, mainly Ringlets, another rank grass feeder. Counts in the uncut meadow and pasture of the adjacent Knapp site produced similar total numbers to last year. The mowing regime in the cemetery is trying to meet a range of objectives, but the changes have shown clearly that if you want urban butterflies you need to cater for the full life cycle.

The Burnet Moths at Jacob’s Ladder don’t seem to have suffered and there were many of them feeding on the spear thistles last week when the sun came out and the wind stopped blowing, their metallic blue red-spotted wings are stunning but they struggle to fly on windy days. The secret of the Burnets’ success on this site is the steep slope which means it is left alone by the strimmers for much of the year. Because of this, there is a healthy population of Bird’s-foot Trefoil, the preferred food plant of the larvae, and the adult’s nectar source flowers Spear Thistle, Wild Carrot and Silver Ragwort. Also, the larvae climb tall grass stems to pupate and so were not affected by waterlogging.

If you create the right habitat for a full life cycle there is a better chance of seeing healthy populations of our natural treasures.

The Big Butterfly Count continues until the 4th August. It is a delightful thing to spend time on, please join in, details are available at https://bigbutterflycount.butterfly-conservation.org/