Saturday, 30 June 2012


Just to continue the debate with Mark and George re the nature of our garden trap sites, here's a photo taken about 10 feet away from where the trap sits looking more or less south west - I can't work out how to add a photo to a comment box.  As you can see there is little between us and southern Ireland.  Exposure also not helped by being at the top of a cliff...

The advantages are the relatively low elevation and being surrounded by water on 3 sides gives a very mild micro-climate when the weather is poor, and I suspect it is a little warmer when the sun is shining because the 45 degree slope below is hardly vegetated and quickly warms up - although that is debateable this year!  The other advantage is that I have a 180 degree open panorama to the south which is probably helpful when there are migrants arriving.  Oh, and a stunning view!

The highest ever recorded wind speed in Wales was logged at the airport met station about half a mile away - something around 120mph.  I was surprised that the record wasn't from one of the Snowdonia peaks, but there you go!


  1. As with any site or locale, it's a classic case of swings and roundabouts. Up here, we're mostly spared the extremes of wind, but have more rainfall (annual average approx 1800mm and on average 66% of days have rain in them of some kind) and generally cooler conditions, but see few migrants. I always think that for us to get any migrants up here, you must have to be tripping over the things down at the coast. Strangely, up here the best sites for migrant activity are, seemingly, not down in the sheltered valleys, but up on the hill tops, on sites facing south. Perhaps not so surprising at that!

  2. Here in Cardiff I suppose we benefit from higher temperatures than elsewhere in the county, though it can be pretty windy as it's flat and near the coast. And of course it's urban, so while we get some of the moths that like a warmer climate, we miss some of the species of wilder countryside (or at least I do, Dave tends to get more of these being a bit nearer the edge of the city). For example, I've never had a Hook-tip in the garden (apart from Beautiful, which doesn't really count).

    As you say Mark, swings and roundabouts.

  3. At the GMS AGM, the subject of weather recording was brought up and discussed. As you know, the only aspect of the weather currently recorded on the GMS forms is minimum temperature and some people, myself included, feel that other relavent aspects of the weather should be able to be included on the form, on a voluntary basis, of course. Part of the discussion was concerned with the quality of the recording instruments and the comparability of the readings, most of which I thought of as irrelevant nit-picking, when no one has ever questioned the accuracy of the maximum minimum thermometers everyone currently uses to obtain their minimum temperatures. I feel that all that needs to be recorded are the climatic factors that directly affect the ability of moths to be on the wing and arrive at the trap and these need only be recorded in fairly broad terms, not requiring hundreds or thousands of pounds worth of super accurate weather station.

    1. Hi Mark, Just spotted this post. Not sure what GMS is - is it Garden Moth Scheme?

      As well as running a small (by small read cheap!) met station at home, I have had a fair amount of professional involvement in met stations in the past. I used to work for the environment agency in Water Resources management who run most of the hydrometric network in England and Wales.

      I largely given up using the met station at home because it gives woeful under-recording of wind-speed (about 4x less than it should be I reckon) and also rainfall. The reasons for this are two-fold I think. One is that the equipment itself is not really up to the job, but more importantly the site is not suitable for what is being asked of it. Most people's gardens, unless they have a huge expanse of lawn that is not overlooked by trees or buildings are simply not suitable for measuring those parameters with any reliability at all. That said, it does seem to be much better at measuring temperature, humidity and air pressure. The former two probably do have a significant influence on moth behaviour?

      So, to cut a long story short your best bet might be to measure min temp and humidity, but probably not other parameters. You may also find that reasonable approximations can be made from the hydrometric network data compiled by the EA that would negate the need for measurements at each site. Theirs is run to the relevant british standards which takes a lot of the uncertainty out. If anyone wanted to do some research into meteorological effects on moth behaviour then I believe you can get the data for free for that purpose.

      Hope that perspective helps!