Had a bad attack last week and lost 8 hens to what appeared to be a feral cat. Clear Cat tracks in snow around coop and entry point. It chewed the backs of their heads on most birds. Was looking for an ultrasonic protection from all but birds. The area is netted and now 1/2" wire cloth is put up in the point of entry...Grrrr !!!! Any luck with ultrasonic stuff ??