In the last week or so there has been a noticeable drop in temperature, which for certain species will be a trigger to start moving or increase their food intake to allow them to migrate. It’s a little early for species to start hibernating but no doubt some insects will start to think about it, especially if the temperatures remain as they are.
On Saturday we held a bat and moth walk where we walked a short loop over the dam and through the sculpture park. The cooler conditions were a little worrying as bats and moths wouldn’t come out if it was too cold, as the moths need energy to fly and bats need moths (and other insects) to feed on. It was perhaps unsurprising that we found most bats along the river hunting for insects. The tree cover made it sheltered and created a warmer micro climate allowing the insects to come out.
Pipistrelle and daubenton bats over the River Vyrnwy
We were treated to good views of daubenton bats flying very close to the water as they look to pick insects off the surface. Above them, soprano pipistrelles were ducking and diving catching insects from closer to the leaves of trees and were a constant noise on the bat detectors. Feeding in these locations, at differing heights, means they are not competing against each other for food. Using our thermal imaging scope the bats could be seen zipping around, similar to the video above which was taken a couple of years ago along the same river. We all learnt the collective noun for bats, which can be a colony of bats or the slightly nicer sounding cloud of bats. So the cloud of bats over the river kept us all entertained for quite a while before we started to feel the chill in the air.
We also had brief ‘calls’ from common pipistrelle on the bat detector and finished with a couple of brown long-eared bats hanging under our porch preparing to go out on a nights hunt, probably trying to warm up!
Small tortoiseshell and small white butterflies enjoying the buddleia and warmth
There have been a few nice days with warmth during the day and the buddleia bushes outside the RSPB shop have attracted all sorts of insects from butterflies to hoverflies and the honeybees that nest in the office roof. Butterflies seen have been: peacock, red admiral, small tortoiseshell, painted lady, small white and green-veined white. The odd moth has also be attracted with a couple of sightings of the fascinating hummingbird hawk-moth which, like the painted lady, is a migrant moth that arrives in the UK from Europe in varying numbers each year depending on breeding success and weather.
Flocking house martins and swallows at Lake Vyrnwy (archive photo)
Birds have clearly started to move with the changing weather and this was emphasised with the presence of 250 house martins feeding around the dam on the 15th August. At one point they were mostly landing on the dam wall giving good views which enabled us to see that the majority of birds were this year’s juveniles. There are house martin colonies in the general area but not enough to produce this many birds, so these must be birds gathering together as they head south and taking advantage of good feeding areas. Swallows will be doing similar and at this time of year you often see telephone/electricity wires covered in rows of swallows and martins, bursting in to life when disturbed.
Swallow on nest
However, there is one pair of swallows that are not on the move and that’s because they still have a nest with eggs to attend to. They are in our porch and is their 3rd nest attempt of the year after succeeding to fledge 4 chicks in the first nest and failing on their 2nd attempt. It is typical for swallows to have 2 or 3 broods each year and given how late it’s getting probably shows the abundance of insects that are around as they wouldn’t attempt to nest if there was no food source for the chicks.
Gavin Chambers, Warden
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