Butterfly Musings by David Laurie & Cath Robinson

Butterfly transects
By Cath Robinson

I’m sure many members may well already walk a transect, but I thought it might be of interest to share
my experience. Clearly there is an increased interest in moths in the society since lockdown: Anyone
who is a member of the Whatsapp group will know that Nick has a wonderful wall at work which acts as
a moth trap, and I know at least 6 members who’ve bought a moth trap since March!
I’ve been a member of Butterfly Conservation for many years but it took until last year for me to summon
up my courage and confidence to volunteer to do a butterfly transect.
There has been some form of butterfly monitoring system in place since 1976 but it has been
coordinated by the UK Butterfly Monitoring Scheme since 2006.The UKBMS receives information from
three survey techniques; the weekly transect walk; a specialist species survey for eg. the Swallowtail,
which is only performed during their flight season; and thirdly the Wider Countryside Butterfly survey.
The dataset that this information provides is one of the most important resources for understanding
changes in insect populations and supports work to ensure the promotion of biodiversity.
Essentially, a transect walk involves walking a defined route weekly from 1st April to 29th September
between certain hours and recording the number and species of butterflies seen along the route. There
are environmental stipulations of temperature, wind speed and ideally sunniness. And there is an
opportunity to record other species including moths and dragonflies.
At the beginning of this year the start was delayed by lockdown but as we were able to travel a bit more
I was able to start doing my walks, so in the end we really only missed out on the beginning of the spring
species. On one occasion I saw no butterflies but did see 2 day-flying moths. Recently the numbers
have picked up as the summer bird watching quiet season is matched by the peak butterfly season.
“The June gap” of butterfly scarcity reflects the pause between double –brooded butterflies (like Holly
Blue or Comma) which are waiting for the second brood to emerge and also awaiting the arrival of late
emerging single brooders like Meadow Brown and Gatekeeper.

Large Skipper Small Tortoiseshell
What I have found most interesting is watching the seasons roll past. Each week the flowers have
moved on a little bit: the orchids emerge, flourish and then gradually fade. The birdsong has faded a
bit: the middle day timings of the transect walks are not the best for birdwatching but even so I have
seen and heard a wide variety of species. The spring butterflies have gradually disappeared but now
new butterfly species appear each week in increasing numbers. What I hadn’t anticipated was just how
much change there could be from one week to another. One week I saw 15 Small Tortoiseshells but
the next week I saw 3. Meadow Browns went from 14 one week to 53 the next. What transitory lives
they lead: Some butterflies will have emerged and died between my transect walks. It can be a bit
sobering: all that effort: egg, caterpillar, pupa and then adult stage: poof! [Although not for a scientific
journal, maybe they were happiest as munching caterpillars rather than their brief flight episode, frantic
to find a mate. Who knows?]

Nothing to do with birds but . . .
By David Laurie

One of the pleasures of spring is the appearance of the early butterflies, and one of my
favourites is the Orange Tip. The males have that cheerful splash of colour on the upper
wing and, when they perch, both sexes reveal a beautifully mottled underside. To
encourage them I’ve grown some Garlic Mustard in the garden. It’s a favourite plant for the
caterpillars and though they are well camouflaged I managed to find a few munching the
seedpods. With luck one or two will make it to adulthood. It’s nano-conservation, but taking
my cue from Greta Thunberg I’m hoping no action is too small to make a difference.
By now the Orange Tips are over for this year, bird song is fading out, but high summer
brings its own gift of enjoyments. These include Skippers in the grasslands and sunny
glades with Speckled Woods basking or spiralling in the light.

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