But of course that doesn't take into account recording effort - there was a lot more trapping done in the mid naughties, so this one takes into account the number of 'trap nights' in each year.
I'm no statistician, but it looks to me as thought the pre 1995 data should be excluded from any further analysis (which makes some sense in terms of GMRG's formation etc), but also that Large Yellow Underwing is being recorded as frequently now as ever. Perhaps more useful are the next two, which show the number of individual moths, weighted against trapping effort.
I'm surprised recording has dropped off so much since the mid 2000s - I thought there were more of us trapping than ever. But maybe we're just not getting out of our gardens as much as Jake and Mike did back in the day...
ReplyDeleteGeorge
I'm surprised both show an apparent increasing trend given all we hear about massive declines in many common as well as scarce species.
ReplyDeleteThat surprised me too. I wonder if the 2 species chosen are relatively unfussy in their climate/habitat/food plant requirements, or are comparatively well suited to the agri desert conditions we now have?
ReplyDeleteYou could be on to something there, Adam. As a professional gardener, when mowing lawns, I see no end of Heart and Dart and Square-spot Rustic coming out of the grass sward and in the longer (slightly) grass areas, Large Yellow Underwing too.
ReplyDeleteIt may be that as long as there is grass, with suitable herbaceous species included or nearby, these species seem to get by.
I will take a look at some other species in due course to see if there is a similar trend, but bear in mind I'm not a statistician, so my method could easily be flawed!
ReplyDeleteAs for the change in recording effort I can also look to see if there are any obviously missing recorders. It may simply be that I need to chase more people for records.
Resetting the historical timeline from 1980 - which we used as the historical default for the book and was also used by other counties and organisations - and resetting it to 2000, which now seems to be the new baseline used by many people for recording. Pre1980 Glamorgan records are fragmented into periods of intense recording (1880s to 1930s) or long periods of inactivity, especially pronounced from the mid 50s to the late 80s. With the exception of a few Rothamsted traps and people like Basil McNulty, who lived on Gower plus a few visiting entomologists, moth records are few. As stated, 1995 and the formation of the GMRG, was certainly the start of a period of great activity within VC41. Many species thought to be local or scarce were in fact commoner than previously noted, especially upland species, which were very poorly recorded. MCP & myself, with the help others, notably the late Stefan Golaszewski & Dave, did a lot of trapping during the period 1995-2005 in the eastern half, as did Barry & co in the west. The primary source of records now comes from static garden traps and a few observers, mainly in northern districts, who venture out to record their local habitats. I would very much like to see more trapping done at the major NNR's as I believe there is a whole lot of species which are still considered rare in the county, Portland Moth & Acleris permutana for two, which may be under-recorded. MCP & myself are considering doing places like Merthyr Mawr & Kenfig in more detail, time & good weather permitting. As for H&D and LYU-w, these will always be in the top 10, how about choosing a few species not normally caught in garden traps and see how that pans out.
ReplyDeleteGood article anyway Dave.
Interesting you should mention Acleris permutana. I've had quite a number of what I thought were Garden Rose Torts of the form that looks v similar to permutana(one of which Dave dissected to check, which as it turned out was GRT). Should I be getting more checked or would that not be a good use of time?
ReplyDeleteMight there be some merit in having a debate about which non-garden sites could/should be trapped, and who is willing/best placed to get there? Basically to agree where would we get most benefit. I too can get to Merthyr Mawr and Kenfig without too much trouble for example. Just a thought.
While trapping effort seems to have dropped off since the mid 2000s, it's worth bearing in mind that we probably have more regular trappers than any of the other Welsh counties (even if most of us don't get out of our gardens much).
ReplyDeleteI'd certainly like to do more trapping at Merthyr Mawr, Alun Valley etc, but with a baby due in February I'm not sure 2013 is going to be very productive for me.
George
Believe me George, you'll be glad to get out of the house!
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