Our grandkids, enraptured, got a close-up look at a rescued bald eagle. They were even allowed to touch him. As the zoo volunteer told about the powerful bird perched on her arm, I was surprised to learn this male had a wingspan of about 6 ½ feet, yet because of its hollow bones it weighed only about eight pounds.

This reminded me of the majestic eagle I had seen soaring above a lake, ready to swoop down and snatch its prey in its talons. And I pictured in my mind another big bird—the spindly legged blue heron I had spied standing…