Reducing bird predation - Introducing the ‘Moth-trap ShepherdTM’

Anyone who runs a moth trap at all regularly will know that sinking feeling of looking down into the trap and seeing a scene of carnage - discarded wings and mutilated moths caused by birds who quite reasonably look upon the trap as an ideal source of food, especially in the nesting season. Once they have discovered the trap, then little will dissuade them to stop visiting this handy avian restaurant. I have rigged up all sorts of bird scarers over and around the moth trap - foil, old CD’s and the like with little effect. I also tried packing the trap really full of egg boxes to give the birds little room for manoeuvre, it helped a little, but didn’t really eliminate the problem.

I already had an embryo of an idea to address this problem when I attended Mike Hall’s Norfolk & Norwich Naturalists Society presidential address at the John Innes institute. Mike mentioned that during his years of survey work, it had become his practice to get up before dawn to get his traps in before the birds awoke. I have never been at my best at such hours and wondered how I could close off the trap remotely and preferably automatically.

I’m sure that given more knowledge of electronics than I possess, then a more elegant and high-tech solution could be devised, but I present here my low-tech, ‘cheap and cheerful’ Moth-trap ShepherdTM that has been working well on my aged Robinson-pattern trap for the past two seasons without a hitch. The whole project took only about an hour to assemble and get working. I am hoping to make a version to work with my Skinner trap this year as well - the principle should be easily adaptable.

You will need a wind-up alarm clock, some galvanised mesh, fishing line and a few pieces of meccano. The clock needs to have separate winders for both clock and the alarm. The best sources for these and the meccano are friends, charity shops or ebay. My clock cost the princely sum of £2. Due to the variety of clocks it is not possible to present a single design. I will do my best to describe how I made mine and hope that the attached photos will help as well.

I mounted the clock onto a meccano base plate and then rigged up a simple mechanism that will take the motion of the alarm winder as the alarm is triggered and wind in the fishing line that is attached. The other end of the fishing line is fixed to a small piece of bent wire formed into a hook. The galvanised mesh door is suspended from two wire loops fed through small holes drilled into the base of the lamp holder. Due to the vagaries of my wiring system, mine has a small notch in it to allow the panel to close flush. A long loop of line is then attached to each side of the mesh and the loop fed out through the central cone. Some experimentation will be needed to get this the correct length so that when the line from the clock is hooked on to it, the panel is hanging loose and not obstructing the inlet.

In operation, the clock is wound (both alarm and mechanism) and the alarm time set to just before dawn. The clock is sited inside the trap at the edge. The line with the small hook then runs through a tiny slot cut in the rim edge of the Robinson trap, the clear cone is fitted over and the light funnel sits on top. Engage the hook from the clock line onto the loop from the mesh door and you are hopefully all set. Remember to check that the alarm ‘on/off’ button is in the ‘on’ position - this has been my the only source of failure with this system!

Come dawn the alarm is triggered, any birds nearby will be scared off by the alarm and the mesh door will rise up and block the entrance. Result - live moths, happy lepidopterist and birds forced to forage more naturally.

With the Skinner trap I envisage using a long mesh panel hinged over the central linear entrance and using a similar mechanism to that described above.

As I’m not sure how well the photos will reproduce here, I will be posting a selection of them soon in glorious colour on my website at www.goldswift.co.uk - just follow the ‘articles’ link. I would be happy to post photos of your versions or other ideas there too.

Clive Sheppard