Following my last blog about the epic migration of the Monarch Danaus plexippus in N and Central America which I have never actually witnessed, though I have been told about it by friends, I thought I would talk about another similar butterfly migration that occurs here in Europe though on a smaller scale - that of the Painted Lady Vanessa cardui. This are one of the most widely distributed species of butterfly on the planet and can be found on all continents except Antarctica and Australia. These migrations are now known to start in sub-Saharan Africa and move northwards in spring and summer in generational waves to well within the Arctic Circle. Here in the UK, every ten years or so the migration can be spectacular. The most recent was in 2009. Talk to any butterfly watcher here and they will recount their amazing memories of that year.
year it started for us on the morning of 24 May when Lynn and I were visiting a clearing in Bentley Wood in the west of Hampshire looking mainly for Argent and Sable moth. We became aware of things flying past us at great speed. It was only when a third flew past a bit closer and in the same direction, due north, that I realised it was Painted Ladies. We saw about fifteen that day and all were on a mission. But it was the next day when visiting West Down, Chilbolton overlooking the River Test that we realised the scale of what was happening. To be fair it wasn't entirely a surprise as we had heard from friends in Spain a few weeks before saying that there were unprecedented numbers emerging from an earlier wave of immigration heading north out of Africa and that we should be on the look-out. Back on West Down the numbers were impressive so we decided to do timed timed 5 minute counts across a 50m strip of open ground. At 2pm the count was 600 per hour. At 3.50pm count was 840 per hour all flying due north. The only ones we saw were flying at just above ground level though I have to say that we weren't looking for others flying higher up. This was game on - on a scale I had never witnessed before. This wave had all moved through within another two or three days leaving others behind to lay vast quantities of eggs on fields of thistles where these were encountered on their journey north.
We now know from research papers that had been published in the previous couple of years that Painted Lady can cover vast distances at high level when the winds are in a favorable direction.. It has been proven using vertical-looking radar that the butterflies do this at altitudes up to 1,200m.
You can read more about this in Pete Eeles fabulous book on British and Irish butterflies pictured below. This book took ten years in the making and the standard of photography and the level of detail drawn from personal observation, new science and long-forgotten texts from very talented lepidopterists of past generations make it the best book of its kind anywhere in the world. If you don't have it already you most certainly should. You can read the reviews and purchase it here.
You can read more about this in Pete Eeles fabulous book on British and Irish butterflies pictured below. This book took ten years in the making and the standard of photography and the level of detail drawn from personal observation, new science and long-forgotten texts from very talented lepidopterists of past generations make it the best book of its kind anywhere in the world. If you don't have it already you most certainly should. You can read the reviews and purchase it here.
Later in 2009 Lynn and I took a short break in in Crete arriving on 13 October and noted small numbers of Painted Lady in the first three days of our stay near Chania on the north-west coast. On 16th October we were at the top of the Topolia Gorge, one of several gorges in western Crete that run in a north/south direction, searching for Cyclamen hederifolium and the diminutive Narcissus serotinus when we became aware of a steady stream of Painted Lady, about 60-80 per hour, flying south along the road towards the gorge at 4pm in the afternoon.
Topolia Gorge © Jimzoun, CC BY-SA 4.0
The next morning at breakfast in the mountains at Milia increasing numbers were seen, again all heading south, in the early morning sunshine until 10am when it became overcast with drizzle and the migration stopped. The maximum count was 100 in 5 minutes across 50m. A few were seen later in the afternoon flying in light rain but no further migration was noted that day.
On 18th further southerly migration was noted all morning and a count at the northern end of the Topolia gorge produced a rate of 400 per hour through the gorge at midday.
On 18th further southerly migration was noted all morning and a count at the northern end of the Topolia gorge produced a rate of 400 per hour through the gorge at midday.
Kermes Oaks on Mt Ida, Crete © Tim Norriss
We met up with friends Henry and Felicity Edmunds on 19th October, our last full day on the island, and they kindly took us out to the slopes of Mount Ida (Psiloritis) in the centre of the island. Whilst enjoying a wonderful picnic amongst the Kermes Oaks, a five minute count across 50m at 2.15pm produced 26 cardui (312 per hour) all heading determinedly due south. By 4.30pm we were down on the south coast at Agios Galini and hundreds of cardui were found nectaring on flowering Tamarisk trees on the beach. Despite the numbers present no visible migration was seen and we speculated that this was due to an unwillingness to set off over the sea that late in the day. By 5pm they had gone to roost among the Tamarisk. We like to think that they made the flight safely across the southern Mediterranean to Africa over the following days, perhaps even the following morning.
Agios Galini - Tim Norriss
But the odd thing about all this is that it was not until about this time that people realised that there even was a reverse migration of Painted Lady and most books stated that it didn't happen and wondered why the species hadn't died out. So much great science has been done in recent years. We now know that migrant moths will fly up to several hundred feet at night to test if the winds at altitude are going in the right direction and if they are not they will come back down to ground level and try again the next night. There is no reason to suppose that exactly the same thing happens with butterflies.
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