As an aside, a previous Post Master kept koi carp. We had a very active heron (I lived about half a mile away and saw it frequently). He netted the pond, heron walked on the net, then struck through it.
So Bernard got a fibreglass heron to put next to the pond, so that the real one would avoid trespassing on another’s patch. When he looked a couple of days later, there was the heron using his fibreglass replica as a convenient perch to plan his attack. The heron eventually ate all the carp and moved on.