Monday, November 16, 2009
I WAS working down at the bottom of the garden the other day, converting a fallen tree into logs for the fire. It was one of those pet November days, hardly a breath of wind, and enough sun to make me take my jacket off.
I was enjoying a break in the strenuous labour, and admiring how the sunshine was accentuating the dusky yellow of the autumn leaves on a hazel, when one, large leaf abruptly changed colour. A magnificent, red admiral butterfly landed on it and opened its wings.
These days, we’re becoming more used to solar power. Our parking meters have photovoltaic panels on them and house roofs are growing solar water heaters. But nature has been collecting solar energy for a very long time.
The wings of the butterfly are, obviously, used for flying – and red admirals fly long distances, including wide stretches of open sea. But the wings have a secondary function as solar collectors, and this butterfly was spreading its wings at just the right angle to make the most of the autumn sunshine. Although this species is one of the largest and most handsome in this country, I noticed that the predominant colour on the upper surface of the wings was black – the most efficient colour for absorbing sunlight. When it closed its wings, the undersides were speckled brown, perfectly camouflaging it as a dead leaf.
It chose to land on a leaf that was tilted at the right angle to catch the low rays of the sun. But that leaf, like all leaves, was also an example of one of nature’s solar panels. Collecting solar energy is an idea with a long pedigree. It’s believed that dinosaurs could open up great, sail-like fins to catch solar radiation.
Red admirals have always interested me and I get to see a lot of them in the autumn, because I normally have windfall apples lying on the ground and these butterflies have a passion for over-ripe fruit. An undamaged apple is not much good to them, but if it starts to rot, or if it’s pecked open by blackbirds or the cock pheasant, who comes in early in the morning, they land on it and lap up the sugary juice.
The fascinating thing about red admirals is their migration. The conventional wisdom is that they originate in North Africa, produce a generation in France or Spain, and this generation then travels on to Britain and Ireland. Some even continue as far north as Iceland, but there is no return migration, so the purpose of the whole thing is a bit of a mystery.
I’ve always had my doubts about this. I’ve become convinced that some red admirals in my garden are year-round residents, hibernating and breeding here. I have tall, shaded stands of stinging nettles that are ideal habitat for the caterpillars, and I’ve seen adult butterflies in practically every month of the year.
So I was pleased to learn that there is some modern research to suggest that although most of our red admirals are migratory visitors, some are residents. There are even recent observations suggesting that there may be something of a return migration.
The egg, larval, and pupal stages of the butterfly have all been discovered during winter and spring in Howth, in Co Dublin. Also, from at least two spots on our coastline, red admirals have been spotted in September flying out to sea in a south-easterly direction.
So, I watched the magnificent specimen sunning itself on the hazel leaf, and wondered whether it was a blow-in or whether it could be a genuine, full-time, Irish red admiral.
* dick.warner@examiner.ie
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