I have been watching various species of herons for a number of years and noted that they use different hunting methods. Reliably enough that I can often guess what a bird is from seeing it's behavior, before I can get close enough or get it in the binoculars to identify field marks.

Great Blue Herons and Great White Herons, do indeed, stand like statues for hours at a time, waiting for that one good sized fish to swim between their toes. However, other herons - mostly the smaller ones it seems, are more active stalkers. The Snowy Egret, in fact, is hyper-kinetic, dashing in frantic looking circles often around their larger cousins feet. This disturbs the muddy river bottom and brings the tiny crustaceans they prey upon into the water to be snatched up. The Yellow-Crowned Night Heron seems to do a little of both. They will stand in place for a while, but also are often seen stalking slowly down the waters edge, eyes alert for that darting crayfish. The Green Heron also, will stand for a bit, but also will do a rush and stomp, to stir up the small prey that hide in the mud. I haven't really had an opportunity to watch the similarily sized Little Blue Heron hunt. I see them at dawn and dusk and believe they hunt at night.

Also, the Yellow-Crowned Night Heron has a ruby red eye and is a day hunter. All the other herons mentioned above do have golden or yellow eyes, though.

I do find the ideas very interesting though. I can't say I have observed the other species he mentions actively hunting enough to make any judgements. I have watched feral cats and can vouch that they do at times at least use the "spring loaded" type of hunting he describes. They do stalk and sometimes chase, but usually not for a long race. It makes for an interesting comparison with the Great Blue Herons and Great White Egrets who I have seen stalk a fish - for about one or two steps - before that great beak snaps them up!

Anyhow - the list of 4000 iris colors for birds is a useful sort of reference. Often they are not mentioned in the bird books, and are difficult to make out in the photo or drawing and in some cases, such as that ruby red eye on the Yellow-Crowned Night Heron, can make identification easier. That bright red eye is the only obvious characteristic the juviniles share with the adults of that species.

It is late in the summer, and I've noticed that we now have about four to six Yellow-Crowned Night Herons feeding along the bank. Several are adults, and the others are in "that awkward stage of adolescence" - half grey, half brown and spotted! LOL.

Good birding!