This Great Blue Heron chose the inch-deep waters at low tide off the rocks on the northeast corner of the park as its hunting ground this morning. I guess this versatile hunter felt like seafood for breakfast, instead of gopher. It soon nabbed a fish about six or eight inches long. As the video shows, the bird went through elaborate preliminaries. By my count, the bird dipped the fish in water, or dropped it and picked it up again more than two dozen times over two and a half minutes before swallowing its meal. This is typical behavior for the Great Blue, as well as for the Snowy Egret, as filmed here previously, and probably for herons and egrets generally.
Why do the birds do that? The cat and mouse model comes to mind. Domestic cats, according to one authority on feline behavior, seem to play with a captured rodent or bird — repeatedly letting it go and recapturing it — for the utilitarian purpose of tiring the animal out to the point where it can no longer defend itself and injure the cat. Mice have sharp teeth and birds have pointy beaks that could hurt a cat. So, behavior that appears to be cruel play is a purposeful survival tactic on the predator’s part. This model does not translate well to the heron v. fish setting. There is no way that a fish of this size could injure the heron. I’ve looked for studies of this behavior in herons, and the best I’ve found so far is an article from Brazil about cormorants and Green Herons, which suggests that juvenile birds do this with live or dead fish as well as with random floating objects as a form of educational play through which they learn adult skills like hunting and nest building. Feeding was not the primary motive there. Very well, but neither this heron nor the egret I’ve previously filmed spending minutes dipping their captured fish appeared to be juveniles, and the behavior here was definitely a prelude to feeding, not random educational play. Could the bird be making sure that the fish was completely dead before swallowing it? Hard to tell exactly, but this fish seemed to be quite lifeless by about the third or fourth drop and recapture. Why the additional 20 or so repetitions? Was the bird making sure that the fish had expelled all waste material from its cloaca? The repeated dipping might have a washing/cleaning intent. If a reader has more definite information on this topic, please post a comment. Thank you.