Bird killed in rat trap/tunnel

Sadly, I have killed my first bird (and reported it on TrapNZ). The immature blackbird was killed in a rat trap, placed inside a normal rat tunnel, with peanut butter as bait. The hole in the mesh was 4 squares by 4 squares. Please, does anyone know if there are some standard specifications for wooden tunnels, as I am wondering if we need to make the holes smaller, maybe 3 * 3? I was surprised recently when I heard that some trappers were catching/killing hedgehogs in rat tunnels. That made me wonder if the holes were too large.

I add green food colouring to the peanut butter. I can’t find any papers proving this deters birds but many commercial baits state they are green for this reason. I also add cocoa powder and walnuts (if I have old ones laying about.) Both of those were found to be the most attractive to rats in a recent Lincoln field trial.

We’ve taken close to 70 rats in a couple of bush blocks over the last two months and haven’t struck a bird yet. Our traps are tree mounted Victor Professionals with a custom hood, so not boxed. We did get a hedgehog in the lowest mounted of them.

Our group are using mainly Victor traps in standard length boxes (400mm) and weka boxes (520mm). We also put a 35mm screw up through the bottom of the box at the mid point, which stops the traps sliding too close to the box entrance. We’ve caught 553 pests and 3 sparrows during this time. While it’s sad to trap birds we’re doing our best to keep this to a minimum. Hedgehogs have great PR agents, and aren’t as cute as they’re made out, so they’re on our list as well. https://www.doc.govt.nz/nature/pests-and-threats/animal-pests/hedgehogs/

Thanks for the feedback. The screw idea looks very implementable. And with that in mind, maybe I should stop leaving a little taster pile of peanut butter just inside the entrance. Thanks, Paul

Thanks for the feedback Andy. Tree mounted Victors - I had not heard of that, but maybe not so suitable for backyard trapping. Bait adaptation, that is something for me to work on. cheers, paul