On a mild autumn day I might catch a red admiral butterfly taking the last of summer’s nectar, basking in sunshine or flying among the rooftops against a brilliant blue sky. I keep a mental log of my last butterfly sighting of the year, which soon becomes my first butterfly of the new year. Both are always a red admiral.
It wasn’t very long ago that the red admiral was strictly a migrant species here, arriving from continental Europe and North Africa in spring, and leaving again in autumn, our winters too cold for them to survive. Now, owing to climate change, some stay for winter instead of migrating south.
They don’t seem to hibernate in the same way as other butterflies, such as the small tortoiseshell and peacock, which enter a more consistent dormant state. So it’s common to see them on mild, sunny days, delighting those of us looking for a glimpse of spring.
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At this time of year, you might see red admirals on ivy flowers or late-summer garden favourites, such as rudbeckia or Verbena bonariensis. These handsome insects also continue breeding in winter – look closely in a patch of nettles and you may still find their caterpillars sheltering in folded-over leaves.
It’s been a good year for red admirals, and for other butterflies, too – a welcome relief after Butterfly Conservation declared a ‘butterfly emergency’ in 2024, officially one of the worst years on record for butterflies.
Both 2023 and 2024 were too wet and cold for these sun-loving insects, which need warmth to be able to fly and find a mate. Last year, my garden flowers seemed empty and lifeless without them, and the big banks of nettles I walk past on the South Downs were devoid of caterpillars.
But this year has been better, with butterflies and caterpillars everywhere, a sure sign that the hot, dry weather has enabled the adults to disperse, find mates and lay eggs. Yet while the sunshine and dry conditions have been perfect for the adults, the lack of rain may have caused problems for their offspring.
Caterpillars need fresh green leaves to eat, not shrivelled, dry ones. After the drought of 1976, butterfly numbers dropped significantly. This was to do with the lack of rain, rather than the heat, as foodplants dried up and caterpillars starved.
The crash came in 1977 (one year’s caterpillars are the next year’s butterflies, after all), which happened to be a wet summer. Similar, though less extreme, population declines were seen after the dry summers of 1995 and 2018.
In the drought year of 2022, I watched a desperate small white butterfly struggle to lay its eggs on a shrivelled charlock plant, and took the eggs home to raise on a supermarket cabbage.
Fresh new adults emerged successfully a couple of weeks later. That year, ringlet butterflies, which lay eggs on grasses and tend to do better in slightly wetter years, also laid eggs in my garden for the first time, not surprisingly around the moist fringes of my pond.
The wetter years of 2023 and 2024 came after a drought, so there are too many variables at play to know if 2022’s drought contributed to last year’s butterfly emergency. I’m certain it did, but it’s unlikely we’ll ever know for sure.
The truth is, our butterflies have been declining for many years, thanks to a combination of habitat loss and pesticides. And now, climate change is making weather more extreme, and extreme weather more frequent.
The milder winters may be changing the behaviour of our red admiral, even helping it to increase its range and population. But what the future holds is, as yet, unclear.
Read more of Kate's columns:
- It burrows deep underground, has horns like a bull and is named after a terrifying Greek monster – meet this awesome minibeast
- Healthy seas store more carbon than forests – so why is marine rewilding far less common?
- Ancient folklore is being rewritten by climate change. We need to restore balance to the seasons
- “A magical but terrifying adventure.” This Halloween, head out after dark to glimpse a feared and ghostly creature
Top image: red admiral butterfly. Credit: Getty
