Summer World_ A Season of Bounty - Bernd Heinrich [12]
The swamp is dense and I see only its surface. Much remains hidden, and I hardly know of its existence. Today I had the pleasure of making the rare acquaintance of a bittern. This large bird of the heron family may be here all summer, but one would never know it. Today, however, I heard a bittern’s “song,” an unearthly sound that carries for miles; one would scarcely attribute such a strange sound to a bird. The bird’s colloquial name, “pile driver,” is derived from the male’s call, which reminds me of somebody driving a stake into the ground with a large sledgehammer in a large echo chamber. I located the bittern’s brown streaked form only with difficulty, through my binoculars. Standing among cattails on long yellow-green legs, his erect body with elongated neck and bill straight up, he blended in with the vertical dead cattails. He stood without moving a muscle for perhaps half an hour or more. Eventually he started to creep forward, his every motion epitomizing one’s stereotype of the “silent stalker.” He hunched over, gradually lifted one leg, and just as slowly in one continuous motion put it down in front of him and lifted the other. Then he stopped, again frozen in position, until, very slowly turning his head, he took another slow-motion step forward, to again stop for a few minutes and then again take a step or two. Suddenly his head shot forward and down with lightning swiftness, and came up with a frog dangling from the bill. If he had not announced himself (to a potential mate) I would never have known he was near. There is much right under my nose that I don’t see, and thus I look forward to getting out, again and again—to discovering.
The birds have started their summer schedule. If not in flamboyant garb, then in song, they put a high premium on making themselves conspicuous. Like us, they communicate through the senses of vision and hearing, and so we are fortunate to be able to be spectators. Some, like the male red-winged blackbirds who perch on top of the cattails or bushes, make themselves conspicuous to rivals, and possibly mates, by where they perch, by flashing their brilliant crimson epaulets (which they otherwise can hide), and by backing up their visual display with a vocal one. The bittern can stay hidden and rely on vocal display almost exclusively. But whatever the different animals do, I can’t even imagine what summer, and life, might be like without them.
3
Wood Frogs
28 May 2006. IT RAINED FOR A WEEK AND NO INSECTS flew. But today the sun came out and I heard the first gray tree frogs. One male was calling from a branch above the road as I jogged by, and I stopped to find him. He was a gorgeous green (not grayish as suggested by the name). After I climbed up, got him, and brought him home, I put him in a terrarium for a detailed look. He perched on a twig and stayed there like an ornament, but continued to call in three-or four-minute bouts at approximately hourly intervals. When at rest he has a deflated throat that vibrates rapidly at very low amplitude. Then, to call, his whole plump body contracts and suddenly looks skinny, while his loud penetrating churring sound erupts at the same time that his throat balloon inflates.
He produces his loud penetrating calls by exhaling to inflate his throat balloon, and his abdominal contraction is the engine for that burst of sound. With that penetrating sound, his whole body vibrates to its frequency. When my (temporary) pet called, several others within 100 yards of our house joined in. The females, like most other frogs, presumably go toward the loudest, generally nearest,