Winter survival of red admirals

[Padfield]

This topic has come up in the February and March sightings forums (and countless times before) so I thought I'd start a thread where our thoughts on the matter can be collected and perhaps those who have access to the latest research can enlighten the rest of us!

I'll kick off by giving my theory (speculation). I think the northern winter is too long, rather than too cold, for this species. It is often seen now on warm days in February and even March but by the real spring rather few individuals remain, in my experience. A long, relatively mild winter is particularly inimical to a species that doesn't readily achieve deep torpor.

My own data relate to Switzerland, where the winters are typically shorter than in the UK (long before the equinox the sun rises quite high in the sky and delivers a lot of warmth) but cold (in the depth of winter). Red admirals are common winter sightings (in freak warm periods) but even here they are not common spring sightings. Recently there have been marked early warm periods and I have seen more of these winter admirals but I haven't noticed any evidence of breeding to produce a native summer generation.

Some people think the increased survival rate recently is due to a greater availability of winter nectaring plants in gardens.

Over to you!

Guy

[robpartridge]

Hello Guy,

that all sounds convincing to me. A few years ago I had an intriguing sighting of 3 red admirals flying high up and pursuing each other around some ivy-covered poplar trees in mid-May. There had been no reports of migrants at the time and so I assumed that they had over-wintered, but to make such assumptions isn't at all scientific. I have only ever found the caterpillars in late summer; has anyone found broods much earlier in the year in the UK? Presumably finding broods in April or May would suggest successful over-wintering but a close eye would need to be kept on reports from coastal stations,

Rob

[David M]

Maybe there's a strain of Red Admirals that is more tolerant of longer winters? Whatever your personal views are, one thing's for certain - more and more of them are getting through British winters.

[The Annoying Czech]

In the Czech Republic, overwintering Admirals are very scarce, although there are some very early sightings and I myself saw one in April 2010 ( )

They're arriving en masse in early May, if the Spring weather is OK (which usually is). Since they're used to be totally common from May to Autumn (together with Maps, Small Tort's, Commas, Peacocks and Ladies), I don't regret they don't stay.

And unlike Small Tort's, Peacocks and Ladies, they don't fluctuate. Eg. 2011's Peacock generations were far too weaker than 2-3 years ago (which's something I can live with ).

[millerd]

Hello Guy,

Presumably finding broods in April or May would suggest successful over-wintering but a close eye would need to be kept on reports from coastal stations,

Rob

Back in the early 1990s, when I lived in Dover, I found small Red Admiral caterpillars in early May (and successfully bred them through). The idea of overwintering Red Admirals did not appear in any of my books, so I assumed they were the progeny of early migrants. This, however only puts the issue back to Northern France, where the winters roughly are the same as ours, perhaps a bit colder inland.

Dave

[David M]

This, however only puts the issue back to Northern France, where the winters roughly are the same as ours, perhaps a bit colder inland.

Indeed, and this pertains to QOS Fritillaries too. If they are breeding in northern France where winters are broadly similar to those in southern Britain, how come they don't establish themselves definitively over here?

[Padfield]

Indeed, and this pertains to QOS Fritillaries too. If they are breeding in northern France where winters are broadly similar to those in southern Britain, how come they don't establish themselves definitively over here?

A possible answer to that question is that breeding populations in northern France are readily replenished with migrants from further south. It is easier to maintain a population at the limits of a species's ecological range if the population is not cut off from others by a forbidding stretch of water. Obviously, Queens are capable of crossing the channel, but equally obviously they don't do it that often - it does represent an obstacle.

Guy

[Gibster]

This is from Sightings Janaury 2012:

Re: Sightings january 2012

Postby millerd » Fri Jan 13, 2012 11:40 pm

Jack Harrison wrote:Nick's Red Admiral looks so very fresh, I have to wonder if it might have just emerged? do we know enough about RA life cycle? It doesn't seem to have a definite period of dormancy (as eg Peacock).

Jack



To lift a post from the Sussex BC site:

Thursday 29 December 2011

A festive poke around in hamlet nettle beds up the Ouse valley yielded good numbers of overwintering Red Admiral caterpillars. Below one favourable South facing flint wall five were located in just under a metre's length, all much advanced in size compared with previous years

I think that larvae, pupae and adults have all been reported throughout the winter months in recent years. A bit like the Q of S in parts of Europe.

Dave

[Gibster]

I was wandering Epsom Common with Sami a couple of days back in glorious warmth (well, probably 12 degrees or so) when we saw our first Small Tort of the year flying across a field. We both remarked how odd that in 5 hours we'd completely failed to see a single Red Admiral, I've seen 10 already this year.

Perhaps the Red Admirals I've seen during January and February really have "burnt themselves out" with the distinct lack of available nectar and have finally succumbed? Could this be a possible explanation to the dearth of sightings on recent mild days?

Gibster.

[millerd]

Another quote from a post on the Sussex BC site (29th February);

"...Flushed up a Comma whilst releasing a fresh Red Admiral butterfly. This was taken in just before the cold spell and took 7 weeks exactly from pupation to emergence. Most of the other pupae are either deformed or have died, and suspect this stage is their Achilles heel in the overwintering cycle, as in previous years pupation has occurred much later (March to April) when conditions are warmer... "

Dave

[Padfield]

A lot of good points. I'd completely forgotten that the red admiral overwinters either as a caterpillar or an adult - a fact many books fail to mention, though it is well established. A caterpillar that lacks the ability to enter deep hibernation is even more vulnerable to long winters as it cannot fly off on sunny days to take nectar in gardens - it cannot feed at all for the entire time nettles are not growing. However, if the winters are becoming sufficiently mild to allow nettle growth then I can easily imagine more caterpillars surviving. Being feeders, capable of growth and (very limited) repair, they are in a very different position from adults, which essentially run down their batteries from the moment they emerge. Could increased number of spring red admirals be due to an increased number of caterpillars successfully overwintering, leading to adults before the immigrants arrive (and which get mistaken for overwintering adults)?

Guy

[millerd]

A look through the posted pictures of 2012 season Red Admirals on this and the various county BC sites does indeed bring up a few very new-looking individuals...

Dave

[Padfield]

I'm more and more intrigued.

Six out of the seven red admirals I took mugshots of last autumn (to see if I could recognise them after hibernation) had significant wing damage. The seventh showed scratches on its paintwork. Yet the only one I have taken a close-up of this season (on 25th Feb) is almost pristine:



It hasn't had time to pupate since the cold spell but could have advanced sufficiently during the late autumn (it was warm enough for butterflies to be still flying in December) to have pupated and emerged fresh after the freeze, like the only clouded yellow I have found this year.

I did revisit the mugshot site this February but it was a little late in the day and I saw no admirals.

Guy

[MikeOxon]

Might day-length be a factor? It's more important than temperature in the seasonal behaviour of some plants.

Mike

[Jack Harrison]

Guy:

I'd completely forgotten that the red admiral overwinters either as a caterpillar or an adult - a fact many books fail to mention, though it is well established

I had often wondered whether it can hibernate as a larva or pupa but have never seen any details. Maybe I've missed something that has already been said on this thread. What/where is the definitive source that they can overwinter as larvae?

Jack

[Padfield]

I had often wondered whether it can hibernate as a larva or pupa but have never seen any details. Maybe I've missed something that has already been said on this thread. What/where is the definitive source that they can overwinter as larvae?

I don't know about a definitive source but Lafranchis states it in Les papillons de jour de France, Belgique et Luxembourg, as does Tshikolovets in his new book, both without extended comment.

Guy

[Mikhail]

As far as this country is concerned, I believe Mike Tucker was the first to document overwintering by Red Admiral larvae in an article that appeared in the Butterfly Conservation magazine some time in the mid or late 90s. B.C. should be able to trace it. In the Millennium Atlas there is a reference to an article in 1997 which is probably the one. At the time I was astonished to read it, but I soon had the opportunity to make my own observations. In November 1999 I noticed a female ovipositing on nettles at the foot of the Bournemouth cliffs behind some beach huts. I followed the development of the larvae throughout the winter. I see from my diary that I spotted a pupa on 10 March 2000, and two days later I found a fully grown larva at Ballard Down, near Swanage. I have also on various occasions found well grown larvae in the spring quite well away from the coast in places such as Verwood and Ringwood.

Misha

[Jack Harrison]

Another possible piece of the jigsaw puzzle came to me while thinking in bed after a middle-of-the night posting on this topic: larval food plant.

On a recent thread mention was made about Brown Argus moving north and adopting new larval food. In the early part of the 20th century, I believe that the Comma mainly used (often the cultivated version) hops, this being perhaps the best explanation of its curious distribution at that time : hop fields of Herefordshire and Worcestershire and also Kent. No doubt nettle was used then but as a secondary food; today of course it is the main foodplant and is a widespread plant. As the Comma evolved to prefer nettle, it was able to expand its range dramatically.

Now during my night wakefulness, I recalled some experiences from 40 years ago that I had completely forgotten. I used to work in Malta regularly and — naughty, naughty — would bring livestock back to England. I don’t think nettle is a very common plant in Malta (climate too dry in summer) but Pellitory is used. But I never found Red Admiral caterpillars on that. I would find them on Mallow; they would happily feed on Mallow when I got them back home. I could find Mallow leaves for my caterpillars in the depths of English winter. Mallow doesn’t die back to the same extent as do many other plants

So could, at least some, British Red Admirals now be using Mallow (perhaps even one of the cultivated varieties) as an alternative foodplant?

Jack

[Mikhail]

I have never found Red Admiral caterpillars on Mallow, but Painted Ladies regularly. However I do often find Red Admirals on Pellitory-of-the-Wall, which is a common pavement weed in my area, though from time to time the council sprays it, as they think dead plants are less unsightly than living ones.

[robpartridge]

This is a very interesting set of posts; it does seem that this species is, one way or another, on the verge of a becoming a resident as well as a migrant - is there an official definition of 'resident' as far as butterflies are concerned? I was intrigued by those nettle beds way down south, though. Here in the fens of Cambridgeshire all the nettles that I know of die back completely. Only now are the first signs of regrowth appearing, and there certainly isn't room for an overwintering larva to be hiding away.

Rob