Sometimes on the train north to the country, I catch a glimpse of a heron rookery in a swamp by the tracks. To call it a rookery, now a general term for a breeding colony, is to catch a linguistic glimpse of the great colonies of rooks’ nests — raucous, brawling places — that dot the English countryside. What I see from the train should really be called a heronry, a village of well-built heron nests high in the trees. In winter, they stand out against the sky like dense clouds or puffs of dark smoke caught in the uppermost branches.
The recent ice storm left a lot of shattered trees behind, including many in the swamp. But as far as I could tell, none of the nest trees had broken. Nor had the high winds pitched any of the heron nests to the ground. I began to wonder about all the intersecting decisions that go into a heronry.
It begins with the presence of water, which is where great blue herons feed. It requires a certain height in the trees, which means trees of a certain age and branch structure. But do those qualities also give resistance to wind and severe ice storms? Or do the birds prefer certain species of tall, well-branched trees over others? After all, no respectable heron would nest in a birch.
I am used to thinking of evolution doing the selecting — blind, impassive adaptation over millions of years. That is a dispassionate way of understanding behavior. But a heronry embodies a system of knowledge present in these herons, a complete, successful and highly inventive understanding of this world around them. Grasping how it came to be does not make it any less marvelous.
The train rumbles past that swamp a couple dozen times a day. Who knows how many humans have looked up at that heronry? The hard part is learning to see nature as a dense web of interconnected knowledges. We see the dimensions of the landscape, but we miss seeing the fullness of the understandings that inhabit it. I look up at the heronry and the question that stays in my mind is this: What do herons learn from living together?
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