I have observed a South London 'conserved listed' large 30 acre or so cemetery area (wooded and grassland) for many years confined within a dense urban townscape. The Speckled Wood butterfly has always been one of the first butterflies to be noticed in relative abundance during April/May and the last to depart Sept/Oct. This year 2014 few were noticed emerged after our prolonged wet Spring. Alarming to me, they have disappeared completely this mid June which is completely out of character over a decade or more of witness for this species in my observed London area. Perhaps, a second brood might show up again soon. In contract this year we have had an unusual glut of Ringlets present totally out of character and never noted in former observations other than a single spotting in the last couple of years. Marbled Whites have been abundant again this year, while, not over-present in the past. We have had frequent Wasp Spiders - now not present at all save a single one last year. We are concerned about our 'listed area' of flora, etc. not being municipally managed intelligently being that the municipality appears to have no convergence with 'the listing authority'. Comments please.
There may be no 'right' answer here, but here are my comments...
Change can be worrying, but is not necessarily a problem. The vegetative side of the ecosystem is always in a state of flux - bare soil becoming colonized, then the herbs being replaced by scrub then trees. The various states of succession have different denizens in terms of animals, birds and invertebrates. Once climax forest is reached (assuming we are in a temperate climatic zone), change continues on a smaller scale, as old trees die or get blown down, clear patches starting the cycle again and providing rich woodland margins and rotting trunks.
As you have noted, ringlets and marbled whites are moving-in. To me that suggests there may be more open area and/or somewhat different mowing regime for the grass. But in a general sense, that is incidental. You have a familiar set of creatures and plants in your expectations, but they would only persist med-long-term if the site was managed very carefully overall. ...Probably more-carefully than is financially practical, apart from keeping the burial areas mown to a certain length of sward, and that is only part of the ecosystem, of course, though important for the browns (incl. marbled white).
One also has to bear in mind the population dynamics over a larger area. The changes you see in your site will inevitably partly reflect regional changes.
Also, in commenting on the butterflies (and wasp spider), you may be missing the larger picture - the majority of species are less obvious (moths, bugs, flies, beetles, etc.) It could be that the overall number of species is increasing, which one would normally deem as good. It is not an easy domain in which to be objective, and universally useful metrics are difficult to define.
Well, that's just my opinion, and I don't know the site.
I suggest you find the local branch of Butterfly Conservation and get their take on it.
If you do so, I'd be interested to hear how you get on.
Many thanks Mike...
for your valued professional comments to my concern about an unusual and sudden disappearance of Speckled Wood butterflies (from my years of observing) in a South London cemetery being the extensive twinned 'Brockley & Ladywell Cemeteries' of Lewisham. Considering the ubiquitous nature of this butterfly more than other of the species seen over many years are, all of a sudden, no longer noticed mid year in little changed woodland cemetery habitats that I frequent . This butterfly's 'early year 2014 demise' does remain problematic to me even with your most reassuring advice. Perhaps, one should be concentrating on the caterpillars which, I have to admit, I don't tend to search out – only coming across them by accident while looking out for butterflies. I am not aware I have ever spotted a Speckled Wood caterpillar. In considering municipal management – wholly un-knowledgeable and unintelligent as to habitat re when to cut the grass and when not to – rather, a constant strimming and mowing regime that seems to cut and slash (particularly in summer) every other day with potential to cut away flora that invertebrate creatures need to thrive upon in the borough of Lewisham whose conservation remit is lamentably lacking in said cemetery's designated nature listed site.
I am sorry to hear of the Speckled Wood's lack of numbers It belongs to a Butterfly family that normally only feed at night and if in the open in the day drop with the slightest movement, its very rare to see a larvae
As for strimming slashing its unlikely to harm the larvae as they will be well down at the food base or under moss stones. The adults may be missing because the grass is greener elsewhere
In my limited experience there is always a drop in numbers at this time of year we are between two generations
PS Marbled Whites are the same Genus and the larvae have similiar foodplants /habitate so things cannot be that bad
Ah - that cutting regime (if that's not too posh a word for what happens) does sound wildlife-unfriendly; a bit of a 'green desert' situation (though things like craneflies will probably like it).
It is never a bad thing to have observations. We can't make meaningful interpretations without them. If you get a response from BC, you may find they have had smiilar reports from elsewhere (or not; yours could be the first). They may have an explanation of sorts; perhaps in some sites there was a correlation with increased numbers of some parasite (like the small tortoiseshell scenario) or increased use of some pesticide, for instance. That is, there may be an explanation, good or bad.
In any case, I hope the speckled woods return and cheer you up. They are charming denizens of dappledness, and the appreciative's lives are a bit poorer for their absence.
I revisited a different rambling (part kempt and part wonderfully wooded and wild) South London cemetery today and was pleased to spot a single Speckled Wood which type also is drastically down in that location so early in the year. Instead, (as in the other urban London cemetery) Ringlets also seemed abundant that I have never viewed there in previous years. And, what a surprise to witness a Ringlet variant male of which I saw several of the same so distinctive the lighter rear wings in flight that I wondered what I had come across if not a Ringlet?
Sorry to rehash this thread, but I felt compelled to ad my observations as well. Our observations are a great tool in keeping an eye on our natural world, you should definitely contact British Butterflies and I just wanted to post mine.
I am in Hastings East Sussex, and we have seen some odd things in our normal butterfly populations as well. I of course can only speak of my own 'local' patches, but we too have seen great numbers of Ringlet Butterfly this year. Where we would normally only have seen 10 in a day I counted around 50 yesterday. As for Speckled Wood, their numbers are down from last year where we are as well, although I'm still seeing individuals after the 13th, but in general not as many as last year. A local patch I frequent we counted 16 White Admiral where we had only ever seen one two years ago. I have only seen one common blue and no other blues or small coppers where we would normally and in fact, last year's second brood was amazingly well populated. Small Heath is another to have suffered and Grizzled Skippers at two normal locations here we have found none this year.
Lepidoptera are a fantastic tool in seeing quickly what changes (be it to habitat or weather/climate) mean to wild areas. I would wager that our winter weather had winners and losers but played a big part, and that we are seeing that in some lepidoptera species, (there are some moths too showing similar signs winners and losers). The good news is that they are also very quick to recover as we saw last year with the dismal cold spring we had and the second brood (here at least) was busting with species.
As Mike says things are quite dynamic in nature, but I would agree that although the management may not have contributed to what you're seeing, councils should pay better attention to the needs of nature. We have the same problem here adjacent even to SSSI sites councils are contracting for mowing paths for dog walkers' in complete contrast to what nature needs. I saw a recent article here about road side verges and a conservation group urging councils to leave them alone and only cut them twice a year.
Basically we can live in hope!
Good post; interesting observations and thoughts.
Talking about population recovery: I meant to mention that there are multiple drivers for that. For instance:
- In a particular site, a drop in the numbers of a target species may cause the population of its predators to drop, meaning that the following season may see a higher percentage survival of the immature stages, making up for a smaller number of eggs.
- The population of the target species in a site may normally be partly immigrants/vagrants from nearby sites. That can allow the locally-grown individuals to disappear entirely one year (maybe if a vital plant is removed or dies), yet the site can become populated the very next year. A lot depends on the species, because some are great wanderers while others never stray far from their larval foodplant. In mentioning 'nearby sites', I am effectively talking about 'wildlife corridors', which are important for other reasons, too.