Sunday, December 17, 2006

Birds and Tools II

The Green Heron's amazing bait-fishing behavior provides yet another glimpse into the realm of tool-using birds. I've blogged about this in the past, but it's worth retelling. I've not personally observed them fishing in this manner, but I've photographed a lot of Green Herons over the years and hope to witness this fascinating behavior someday. They're always a joy to watch and take pictures of.

The "tackle box" of the Green Heron includes variety of lures, such as crusts of bread, popcorn, even bits of plastic foam or feathers. Some herons have been observed breaking off small pieces of sticks to use for fish bait. The stalking bird purposefully sets its bait in the water and waits. When fish swim over to check out what they think might be a meal, instead they risk becoming one. Green Herons will even dig up earthworms or use mayflies as live bait, which often proves more successful for enticing fish.

While it isn't known if this behavior is innate, learned or a combination, juvenile herons seem to lack the fishing skill and success that adults exhibit at the pond - so, they must improve over time. I can speculate how such an adaptation might have arisen. Imagine a hunting heron's bill over the water and tiny bits from a prior meal drop into the water. Fish are naturally attracted - quick ones get away with a nibble while slow ones aren't as lucky. What may have begun as sloppy eating habits were refined over time into a consistent way of earning meals.

Green Heron images © 2006 Mike McDowell

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