Moth Survey at Highdown Gardens, Saturday 16th July 2016
Survey by: Richard Poxon,
Member of the Society of Amateur Entomologists
This year's survey took place on the evening of Saturday 16th July 2016. Further trapping sessions took place both before and after the main survey evening to capture and monitor other species as well as migrant moths that appeared during the summer and autumn period.
A Robinson Pattern Light Trap was used to attract the moths. A petrol generator was used to power the trap. Around ¾ of the captured moths were released back into the same area at sundown on Sunday 17th thus avoiding any predators that might take advantage of the free meal. Remaining new moths were kept in my garage while identification took place over the coming few days before being released back into the Gardens. The moths remained within their natural habitat.
I try to select a night with favourable conditions although sometimes the moths feel differently and although not an ideal evening I have chosen the evening of the 16th July as it produced a fairly large catch compared with the preceding days. The weather was settled with low cloud cover and an evening temperature of around 17°C. The wind was from the south west at 4kts.
From a moth trapping point of view this summer at Highdown has proven to be reasonably productive. Most of the species now recorded in the species list made an appearance at some stage during the summer months although as is often the case, not necessarily on the survey night. I was unable to report similar numbers to those encountered in last year's survey but I have been able to add 8 new species to the overall count which is fairly satisfying.
Some new moths identified in 2016 include the Female Ghost Moth (left) and the Coxcombe Prominent Moth (right).
The data in the 'core' species list (see below) has been colour coded in 'traffic signal' style to indicate 'red' for those species that were absent 'yellow' for those species who's numbers remained the same and 'green' for those showing an increase. The yellow shaded area at the bottom of the list contains the new species (8 in total) which were not identified in preceding years (not because they were not present in previous years but because I have had more time to sharpen my id skills). Surveys focus on the 'core' list from 2008 but as before I remain on the lookout for any species that don't look familiar in order to add them to the Highdown Species list total which now stands at 189 species to the end of 2016.
So far, it has been a rather interesting year for migrant moths. A very large influx of 'diamond back' moths were seen in the Gardens and all over Sussex during the summer. This species originally believed to have originated form the Mediterranean region has now spread worldwide and is able to migrate large distances during favourable conditions. As well as being rather small it is able to re-produce very quickly and in huge numbers. It has now occupied every continent except for Antarctica and can be a serious pest in crop fields of oilseed rape and cabbage.
Other migrant moths are less formidable and rather more attractive and include the Convolvulus Hawk Moth, one of which was captured in the Gardens in early September (see photo).
Persistent Southerly winds always bring the best migration results and Highdown Gardens is very well placed to monitor movement. Migrant moths crossing the sea will land and rest when they reach land. They may also be attracted by lights from shipping and enjoy the free lift to reach foreign shores although the 80 mile crossing from France is of no challenge to a small moth at 10,000 feet being blown along in a steady 40mph wind. Add to that its 15mph flight speed! It's easy to understand how they are able to travel large distances in a relatively short time. The Convolvulus Hawk is a true master of this and has a normal flight speed of 35 to 40mph! With wind assistance that's 80mph ground speed when at altitude and rather faster than the ferry!
Once again I would like to thank Jo Hooper, Highdown Gardens' Manager and Head Gardener, and Worthing Borough Council for their kind permission to carry out this exercise and I very much look forward to the ongoing survey.