This month I've been in Scotland taking part in a golden plover survey at an existing windfarm. My role in the survey is different from normal though, instead of counting birds and recording their movements, I've been asked to carry out a survey of their prey items, specifically invertebrates and especially beetles.
I enjoy invertebrate surveys, but of all of the types of survey work I do, this is the type which I am most selective about and probably turn down more than I actually do. The fact is, invertebrates cover a huge array of orders, e.g. butterflies, dragonflies, bees, wasps, beetles, spiders, woodlice, worms, slugs, mites, ticks, flies, centipedes, millipedes, ants, bugs, harvestmen, springtails, the list goes on, to say nothing of all of the aquatic and marine inverts, in fact invertebrates account for 97% of all animal life on Earth.
Guides and resources to help with the identification to species level within many of these groups are almost non-existent. Even if they are there identification often comes down to microscopic examination of a specimen in the lab or even dissection and they are therefore very time consuming. So unless a client is very specific about what they want, I usually decline because otherwise I can end up doing weeks of work for free or working late into the night to meet some unrealistic deadline.
When they are spec'd correctly though as with my present survey, they are very interesting and a pleasant change from standing at a vantage point for 8 hours.
The purpose of this survey is to get an idea of the suitability of the site for golden plover based on the presence of their main food items, specifically invertebrates and especially coleoptra beetles and to then compare it with a nearby offsite area of similar altitude and habitat. I don't need to go to species level, I just need to know that it's a beetle or a spider. Phew! I'm in with a chance then......
With this particular survey it's not just about being able to catch and identify invertebrates, it's also about having a knowledge of golden plover and how they feed in their preferred habitats. Golden plover are largely surfaces feeders of terrestrial invertebrates, so the best way to trap their prey items is to use pitfall traps. The plover also like grasslands of a particular sward height, so the traps need to be set in the correct places and not in the middle of a bog or tall grassland.
Over the years I've developed my own method of setting the traps in a cost effective and quick way whilst still complying with accepted methodology and it seems to work pretty well. I return to the traps at two week intervals to empty them and reset them.
One of the issues on a big moorland site such as this is finding the traps again. Taking a GPS reading helps, but at a more basic level a cane with a flag is the best way once you are within 20m of the traps. You can see one of the traps just to the right of the cane, imagine how difficult that would be to find without the cane even with the GPS co-ordinates.
At this time of year the catch is dominated by beetles, mainly of the staphylinidae rove beetle family, spiders, slugs and a few flies.
It can be a bit messy at times, especially when slugs get in the traps as they often do, but it's fascinating stuff and gives me a real insight into the prey items of golden plover in early winter.
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