Friday, August 28, 2020

The 2020 Season at Knepp, and Prospects for 2021...

This should be a tale of great and greater glory, but is sadly a tale of great woe, with a nasty sting in its tale. More woe is to come.

We were expecting His Gloriousness to emerge in fantastic numbers, as post-hibernation larvae had enjoyed fantastic feeding-up weather, from late March through to early June. But therein lies the problem, there weren't that many larvae.

Each winter I follow a number of wild larvae through, in order to measure winter survival / predation rate. However, this winter I didn't manage to get a measurement - the Forestry Commission inadvertently trashed my breeding area (I can't be critical: they left most of the sallows, it's just unfortunate that those bearing my monitored larvae got felled...). The winter was mild and horribly wet, and such winters are fairly disastrous for hibernating larvae, with predation rates as high as 85%.

Ben Greenaway, who was following a large sample of wild larvae in West Sussex, recorded a predation rate of about 80%. Had I known that (we thought the rate was more like 40-50%) I would not have predicted an annus mirabilis.  

In early June, the Emperor then got stuck in the departure lounge, as the weather deteriorated as the bulk of the brood was pupating. That may have done some minor damage. 

The first Knepp Emperors were seen on June 13th. My first sighting was a rubbish sighting, which was deeply ominous as great Emperor years kick off in spectacular fashion. Numbers failed to build well.

We had a short heatwave around Midsummer Day, wherein the Emperor flourished modestly. Then the wheelnuts came off, followed by the wheels. 

His Gloriousity is vain enough to roost in treetop sprays, and ignores the weather forecast. If He was to roost on the sheltered side of trunks and branches He would have survived the late June and early July gales quite well. As it was, He got shredded, and the equally dim-witted females. A number of crippled Emperors were found on the ground.  This one at Knepp -

This one in Sherwood Forest, Notts (which has recently re-declared itself Purple), on July 5th -

Here's the data from the Knepp Wildland Purple Emperor Transect (a 2km long single species transect walked weekly on non-windy afternoons, using a 50m recording box):-

2015 =  112                       
2016 =    95 (adjusted by Basian statistician, gappy data set)

2017 = 117

2018 = 201

2019 = 101
2020 =   61

The net result was a very poor egg lay - seemingly everywhere.

That in itself is not the end of the world, for low levels of larvae tend to lead to low winter predation rates - the tits don't find the hibernating larvae, and the insect recovers.

But Knepp got hit by a double-whammy: the poor egg lay was followed by a horrific drought, during the early August heatwave. The bulk of Knepp's sallows are on former arable fields, they're growing densely together on damaged soils - not on the woodland soils they're designed for. They are drought prone. They wilted badly in 2018, when no rain fell between May 31st and the end of July. But that was after a massive egg lay, so we got away with it.

This year's Knepp sallow drought is an order of magnitude more severe than that of 2018, and occurred after a rotten egg lay.  

No way is the Emperor going to abound at Knepp in 2021.

This is what many of Knepp's breeding sallows were looking like on August 13th - 

The rains then arrived too late. Oddly, sallows in the woods a mile to the north were not badly affected, but there may be other sites in the Low Weald that were similarly affected.  

In all, I think this was the worst Purple Emperor year since 1990, when a mild, wet and stormy winter gave way to a magnificent early spring and May, only for the weather to collapse in early June - probably as the first adults were emerging - Only, in 1990 heatwave conditions returned in mid-July, too late for the adults, and persisted.  

Pray very hard...  We need a wet autumn, a bitterly cold and frosty December to de-tit the woods, a cold winter, a steady non-early spring, a fine May, and a decent June and July. 

The last of the 2020 Knepp Purple Emperors was seen on July 23rd. Elsewhere, sporadic sightings were made into early August, mainly in the north of the Empire, with the final sighting coming from near East Midlands Airport in newly-Purpled Leicestershire on Aug 18th (a female).

The butterfly seems to have done appalling badly at all sites, with the notable exception of Abbots Wood Inclosure in Alice Holt Forest (I'm not sure why, it may be due to an upsurge in recording). In one top grade site, a privately owned wood known as 'Bucks Best Wood', only a single sighting was made.

The message to 2020 is simple: Don't come back!  

Monday, August 10, 2020

Still flying at CFW

Female Purple Emperor seen egg-laying in a Sallow today (Monday 10th August 2020) in Minting Wood, part of the Chambers Farm Wood Complex, Lincolnshire. I also saw a female Purple Emperor in almost the same location on Saturday (8th August 2020), so good news for the future generation!

Thursday, July 30, 2020

From Francis Farrow in Norfolk

In 2017 I spotted my first PE at Beeston Common, Norfolk. Since then we have had sightings of one or two in 2018 and 2019. Last Monday (July 20) I spotted a PE soaring at tree-top height from one group of oaks to another about 20m away and then back again. As it was overhead I could not determine whether it was male or female. 

This afternoon I saw a PE leaving a sallow and fly up into the canopy of an oak next to it. I did see the upper side this time but only as a dark colour so still not sure whether it is male or female. As this is the fourth year of PEs at this location I think they must be breeding in the vicinity, especially as it is the same oak/sallow they are mostly seen in, although we never see them until the final two weeks of July, which seems later than other places.

Tuesday, July 21, 2020

Foreign Sighting

Not the best season here in Odiham, nth Hampshire but did manage one interesting sighting at a potential new assembly point near the Basingstoke Canal, very close to home. Surely can't have overlooked it for the past 2 decades can I? Oh dear, probably.

Anyway as the weather deteriorated was lucky enough to head off to France for a week's fishing in the countryside just south of Limoges. And as luck would have it we were visited on the balcony of our fishing lodge. The owner is now a man of Purple.....

Saturday, July 18, 2020

Better results at CFW - Friday 17th July 2020

Finally got some semi-decent weather this season at Chambers Farm Wood, Lincolnshire, which produced a semi-decent result of 15 Purple Emperors (13 males and 2 females). I was surprised to find that most looked in pretty good condition (wings showing little sign of damage) and it was good to see strong aerial activity from the males, as they manoeuvred around the Oak trees; I have witnessed very little of this type of behaviour this season.  And, just as I spotted the second female, a male flew in and they both disappeared up into a Sallow together, which is encouraging! With a good weather forecast for the early part of next week, perhaps it brings a little more hope for some better results.

Sunday, July 12, 2020

Closure at Knepp

Folks. I'm officially closing the 2020 Knepp Wildland Purple Emperor season down. They've had a shocker (but not at bad as the W-L Hairstreak which has been almost non-existent here).  

There will be the odd one around for the next week or so, resultant from late-pupating larvae, but they are already so scarce that Neil and I are really struggling to see them - and we know precisely where and when to look. 

In effect, don't travel long distances to visit Knepp any longer this year (and the storks have fledged too). 

I just hope the females have laid enough eggs, but as things stand the prospects for 2021 are not good... ... ...

Friday, July 10, 2020

‘Lift Off’ in Lincolnshire

Today, I met up with Dave Wright and Richard Smyth at Chambers Farm Wood, Lincolnshire. From the start the weather seemed against us, which seems par for the course this year; thick cloud with the occasional shower was forecast for the morning, with a brighter outlook for the afternoon. Nevertheless, we persevered and decided to walk down to Little Scrubbs Meadow whilst it was overcast. In an all-too-brief patch of sunshine, lasting no more than a few minutes, we were surprised to get a brief glimpse of a male Purple Emperor flying over the top of the Oaks at 09:20, but, as the sun disappeared, the butterfly quickly settled up in the gods. We pushed on to the meadow and spent some time there whilst conditions were poor, but as the light level improved, we diverted to the southern part of the wood, where we thought our chances of seeing an Emperor were greater. Here we spent the rest of the morning and were rewarded we three further sightings of male Purple Emperors, the first flying around a Sallow, the other two higher up around Oak trees.

After lunch back at the cars, we covered the northern part of the wood, venturing first up to an area known as Fiveways and then beyond to Minting Triangle. This part of the wood was good for White Admiral, Purple Hairstreak and Silver-washed Fritillary, but we didn’t have a single Purple Emperor sighting at all. On the walk back to the car, we had one last look along the main stone track running south and saw a Purple Emperor in the distance circling low to the ground. As we approached it landed on the track and allowed us to get a few photographs.