It may be possible that it will attract a heron if put out prior to May. I read that too. But I had a resident heron that thought he owned the place and I was more concerned with scaring off the current problem then creating a new one.

I actually saw a pair of them start to glide in two weeks ago and then pull up hard and fly away.

If you do not have a big problem right now hold off. If you already have a heron coming in every day don't be afraid of attracting one. You already have the same problem.

Brian