30 Days Wild | Day 4

day 4
Day 4 of 30 Days Wild

Contrary to the forecast of rain overnight, the skies remained clear and lit by the waxing gibbous moon, giving way to a stunning day of bright blue skies and sunshine. The daily census of migrant and breeding birds carried out by BBFO staff and volunteers like myself revealed that no new migrants had moved in overnight – although an Arctic Tern off the North End and a Buzzard drifting over the mountain were noteworthy sightings.

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A lone Dunlin has been frequenting the seaweed-strewn beach recently, although by now most birds should be on their arctic breeding grounds

For 30 Days Wild Day 4, I decided to acquire some moth caterpillars to add to my rearing collection: a mesh-roofed plastic box containing a range of lepidoptera eggs and larvae at various stages of development. My targets for the morning were a trio of moth species for which the larvae are particularly conspicuous at the moment: Lackeys, Yellowtails and Six-spot Burnets.

Lackey Moths overwinter in ring-like clusters of eggs around small branches on their foodplant, hatching out into larval form by April. Lackey caterpillars spend most of their instar phases living in small colonies after spinning silken webs. These webs are remarkable structures that act in a similar way to glasshouses: scientists have recorded internal temperatures of 39’C when the outside temperature was just 11’C!!! The tents are therefore crucial in protecting the vulnerable early instars from adverse weather. As the caterpillars grow larger and larger, they gradually use up all the food surrounding their tent, and loose the need for a silken home. At this stage the brightly-striped larvae begin wandering further afield to munch on damson, willows, brambles and blackthorn.

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A final instar Lackey caterpillar – not too far off pupating! This form of bright colouration is known as aposematism, essentially warning would-be predators that they taste pretty unpalatable!

This year seems to be a record year for Lackeys here on Bardsey – whilst we usually see plenty of larval tents populating bushes and gardens, there are a lot more spread across the island this spring. We counted almost 60 silk tents in the observatory garden alone, which is a little larger than your average tennis court.

Here are a couple of videos of these intriguing creatures…

The above timelapse focusses on a silk web of quite early instar caterpillars going about their industrious work

I’m not quite sure why they do this crazy head-shaking dance, but I am guessing it is some form of predatory response? It looks hilarious either way!

As I mentioned before, besides the Lackeys, I was also on the look out for Yellowtail moth and Six-spot Burnet caterpillars for my collection. Both species are strikingly-patterned caterpillars, and are thus fairly easy to spot too. I found plenty of Yellowtail caterpillars feeding on the various sallows in the island’s withy beds, and the Six-spot Burnet caterpillars were likewise easy to come by: munching on their chosen foodplant – Bird’s Foot Trefoil – along banks and hedges.

I will have plenty of provisioning to keep me busy for the next few weeks! Looking forward to seeing them hatch out.

Late morning I joined Liam Curson – a young birder who is one of the two assistant wardens employed at Bardsey Bird Observatory this year – to check out the island’s barns and outhouses for nesting birds. We were mainly on the look out for Swallows, wagtails and wrens…

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The old farmyard of Lloft Carreg, possessing innumerable nooks, crannies, sheds and pig sties – the perfect spots for a range of birds to construct their nests, including swallows and wrens

Whilst we did find a handful of Swallows nests, most either contained eggs or chicks too young to ring. We did come across a nice Pied Wagtail nest with chicks a week or so old – perfect for fitting with their unique ID tags! We also checked out the Sparrowhawk nest, which now has two eggs, and a Carrion Crow nest with a large chick close to fledging, which we also ringed.

The bright sunshine today has been encouraging a proliferation of insects in the sheltered spots, particularly Green-veined White butterflies and hoverflies. I managed to find a stunning little Picture-winged Fly (Herina frondescentiae) this morning, and the first Cinnamon Bug I’ve ever seen on Bardsey in the afternoon…

Tomorrow is looking like a pretty horrendous wash-out with strong southerly winds, so we’ll have to see what wildlife braves the weather!

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a pretty damp forecast for tomorrow
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