RSPB Mersehead Blog 14th - 20th August, 2021

Having spent over a month as a residential volunteer at Mersehead, it is now my turn to share the highlights of the week on the reserve. I hope you enjoy!

This week, the Tuesday Work Party spent the day clearing litter from the foreshore and dunes, with an area heading east from the main visitor trail to the high dunes being covered.  As well as small fragments of plastic, faded biscuit wrappers and countless pieces of rope the Marram Grass revealed many more buried treasures such as plastic bottles, large containers and broken fish crates.  One item that did a bad job at hiding was a large, inflatable, pyramid shape marker buoy.  Who knows how far this had floated to reach Mersehead?

Beach clean at Mersehead. Photo credits: Paul Radford 

The locally rare Poplar Lutestring moth was recorded during our weekly survey, having only been recorded in Dumfries and Galloway a handful of times. This is an unexpected record as its flight season is from June to early July in Scotland and Ireland, and late May to early August in England and Wales. The survey also produced the reserves third Centre-barred Sallow since 1996 and the first Chevron of the year.

Poplar Lutestring and Centre-barred Sallow moths. Photo credits: Luke Jones

Unexpectedly warm and sunny weather on Tuesday afternoon allowed for our weekly butterfly survey. The survey produced 7 different species of butterfly, with 33 butterfly recorded in total. 23 Green-veined Whites, 4 Small Tortoiseshell, 1 Wall, 1 Small Copper, 1 Common Blue, 1 Large White and 2 Peacock butterflies were counted.

Small Tortoiseshell butterfly. Photo credit: Luke Jones

Peacock butterflies hibernate overwinter by converting some of their blood sugar into glycerol, which acts as an anti-freeze while it sleeps through the winter in a safe and sheltered location such as a hole in a tree. These are one of the first butterflies that we see in the spring, and will then proceed to lay their eggs over the following months. This first generation of the year will then die of old age after living for almost a year. Caterpillars will then emerge from the eggs and will spend some time fattening up on nettle leaves, before forming chrysalides (pupa/ cocoon), and emerging as adult peacock butterflies in August. This second generation of butterflies are were counted during the most recent butterfly survey.

Peacock butterfly. Photo credit: Luke Jones

One of the reserves trail cameras managed to capture an exciting video of a Barn Owl hunting a mouse, which you can view below. The mouse can just be seen dashing about, evading capture.  Using the settings button at the bottom of the video player to view the video in slow-motion (0.25x speed) enables easier viewing of the fast-paced action.

https://www.youtube.com/watch?v=6ZTUTujYMqc

Barn Owl hunting a mouse.

Having narrowly survived the first swoop, there is a short chase before the lucky mouse launches itself to safety through the gate, causing the barn owl to give up the chase. Fortunately for this mouse, field voles account for 45% of total British Barn Owl diets, Shrews 20% and Wood Mice only 15%, according to the Barn Owl Trust. Barn Owls also hunt for House Mice, Brown Rats, Bank Voles and Pygmy Shrews.

Proving to be a popular spot for owls this week, a Tawny Owl was also captured on video by the same trail camera, perched on a fence post. Owls often hunt from exposed perches such as fence-posts (of which there are plenty across the reserve), and also while flying low and hovering. This gives them a real birds-eye view for hunting, although owls rely mostly on their excellent hearing to locate prey. During the winter, owls will use fence posts and other perches more often in order to save energy and to reduce heat loss that results from flying in cold air.

This week has seen the construction of numerous possible new hunting perches for the owl, with a new fence being installed around the merse (salt marsh) ready for grazing to begin. As with the grasslands and wetlands that are grazed by cattle on the reserve, the merse will benefit from the uneven and selective grazing of the herds. The creation of an uneven sward height and bare muddy areas will benefit breeding waders and invertebrates come next spring. Curlew and Redshank in particular (priority species) will benefit from this grazing as they can hide behind tussocks of grass, sedge or rush to evade predators, and a short grass-sward height enables them to see incoming predators sooner.

Luke Jones, Trainee Warden.