I went back and on April 19 and photographed the roosting sites from another angle and was able to get closer to the birds. The junction of the eye and beak area is quite beautiful. I noticed that the one nest may have had a juvenile, but it was sleeping and didn’t put its head up making it impossible to confirm.
As you can see in the photo, I spotted three nesting grey herons (Ardea cinerea) in an irrigation pond near my house. The pond is right next to the busy 171 highway and I was surprised to see them nesting there. After a little research, I read that the grey heron is very adaptable to urban environments. It is certainly quite common in Osaka as I see them often. They reminded me of the blue heron from North America. The grey heron is commonly found in Europe, Africa and Asia.
I will go back and see if there are any eggs and if they are there all the time.