What’s flying today on the Great Fen?

Emperor dragonfly {Anax imperator}, female laying eggs, Cornwall, UK. April 2010. - Ross Hoddinott/2020VISION

This month marked the resumption of some of our public outdoor events. Over the weekend, I led a couple of small guided walks in the Great Fen, hunting for dragonflies.

The term ‘dragonflies’ is now used to describe both dragonflies and damselflies, and as over half of the British breeding species found in the Great Fen, it is a wonderful place to learn more about them. It is always a great privilege to be able to share the knowledge and experience that I have built up over the years, and more so when it is about dragonflies, a subject close to my heart.

The hot weather was offset by a cool breeze, which kept the smaller insects at bay but allowed the stronger fliers, such as the dragonflies, to put in a good performance. Sites like the Great Raveley Drain, at the end of the track past our Countryside Classroom at Ramsey Heights, provide good opportunities to see a range of species. Setting up territories on yellow waterlily pads were red-eyed damselflies and the more recent colonists to the country, small red-eyed damselflies. A walk across the bridge into Woodwalton Fen National Nature Reserve, provided yet more species in the shelter of the reeds and the trees.

Both guided walks took place on Sunday, one in the morning and one in the afternoon, each with a maximum of 6 people. The morning tour produced a list of 10 species of dragonfly, and the afternoon, 12. During the cooler morning, many insects were still warming up, providing good opportunities to photograph them, and to watch them basking in the sunshine as it came out from behind the clouds. Other insects were also becoming active.

Some insects were spotted only after the twitch of a leaf lead to a closer inspection of the vegetation. Use of a bat detector helped to find insects such as bush-crickets. Species discovered included the dark bush-cricket and the Roesel’s bush-cricket, the latter being a species which sings at a higher frequency and so without the assistance of the detector, not audible to all. The short-winged conehead, a species of brush-cricket that likes the damp conditions of the Fen, was occasionally seen, vivid green in colour and difficult to see at all, if they did not move. The females were seen, with their long, blade-like ovipositors, which they use for laying eggs.

Short-winged conehead by Henry Stanier

Female short-winged conehead, resting on a reed leaf. Long antennae identify her as a bush-cricket, rather than a grasshopper. By Henry Stanier.

As things warmed up, the dragonflies started to become more active. The numerous male ruddy darters, a stunning crimson red in colour, were, as the name suggests, darting back and forth along the paths. Above them, migrant hawkers glided and turned acrobatics in the hunt for prey. As we approached the shade, there in the shadows, a solitary southern hawker slowly patrolled the edges of the shrubs. The lone-wolf of the dragonfly world, this species is rarely seen in the company of other dragonflies. While other species confine themselves to the sunnier parts of the Fen, the southern hawker is adept at hunting in the late evening or in the shade, monopolising the insects its relatives don’t catch.

Southern hawker male by Henry Stanier

Southern hawker male by Henry Stanier

Male southern hawker, identified by green spots on abdomen, turning blue bands at the end. By Henry Stanier.

The trees provided another opportunity to seek out a particular species, the willow emerald damselfly. This new arrival to the country lays its eggs in willow-tree twigs, over water, the larvae later hatching and dropping down into the water. Five years ago it would not have been found here but now, in the course of one walk, several were seen. This included a male and female in ‘tandem’ the male holding the female firmly behind the head, guarding it against what he considered was unwanted attention from other males. This species is one that emerges later in the year than most, and so there will be plenty of sightings yet to come. Other species are at the end of their ‘flight-period’, the adult phase of their life, such as the four-spotted chaser. This dragonfly is abundant in June, but now sightings are few and far between, with only one individual being seen all day.

Also on the wing, were various butterflies; large skippers, brimstones, peacocks, small tortoiseshells and meadow browns, and of course, in the treetops of the oaks, purple hairstreaks, dashing back and forth, defending their lofty territories. Standing out quite conspicuously against the weathered wooden boards of the Rothschild bungalow, was a very large moth which, once it took flight and revealed its red underwings, revealed its identity. The red underwing then did a circuit of the bungalow, returning to the same side of the building. This time its wings were slightly parted, affording a better view of the stunning, yet normally hidden, colouration of its hindwings. A common lizard was also seen basking on the steps of the bungalow, an added bonus for the photographers.

Red underwing by Kate Bailey

Kate Bailey

Red underwing at rest on the side of the Rothschild bungalow. By Kate Bailey.

The species list for the day was a satisfying one: blue-tailed damselfly, small red-eyed damselfly, red-eyed damselfly, azure damselfly, common blue damselfly, emerald damselfly, willow emerald damselfly, common darter, ruddy darter, four-spotted chaser, black-tailed skimmer, migrant hawker, southern hawker, brown hawker, and the Emperor.

The bat detectors will get more outings later this month, including the last Saturday of August, always International Bat Night. So, once again, the Wildlife Trust will be running a guided bat walk and bat survey at Woodwalton Fen National Nature Reserve.

Henry Stanier (Great Fen Monitoring and Research Officer)

Emerald damselfly at Woodwalton Fen

Emerald damselfly by Henry Stanier

Male emerald damselfly, showing blue colouration behind wings and on the tip of the abdomen.