SUMMER WORLD
- A Season of Bounty
- By Bernd Heinrich
- Ecco, 253 pages, $34.99
Why does the custom of making linseed oil usually involve a dash of onion, and why must white wine go with fish, not meat? Could the answers help explain why the lovely little bird known as a red-eyed vireo almost always steals a piece of the nest of a paper wasp in order to decorate its own?
These are the kinds of questions Bern Heinrich asks in Summer World, the sort of book that brims with the marvellous and mysterious things you will find in the familiar and the close at hand. It's all about paying attention, and in this book, that's what Heinrich does. He pays attention to summer.
Following his popular Winter World: The Ingenuity of Animal Survival, Heinrich's method of interrogating summertime is sometimes a matter of "walking around and aimlessly gawking" in the environs of his home down a dirt road in Vermont, or making forays into the woods from his cabin in Maine. Sometimes, he just sits quietly in the branches of a pine tree at the edge of a bog, at dawn, watching.
But Heinrich is no idle nature boy. He's an accomplished scientist, and his attentiveness sometimes leads him to hilarious little experiments, like putting bloodroot flowers into his fridge to see if their petals will close or stay open, or wading around swamps to take the temperature of the clusters of frogs' eggs.
The whole point is to explore summertime's mad dash of renewal and reproduction after winter's long hiatus of hunkering down and making it through. When his experiments require the acquisition of wasp nests, things get downright slapstick. This is how linseed oil recipes and white wine come into it.
Crows don't like wasps any more than blue jays, chipmunks, mice or red squirrels do. This appears to have been true for so long that an astonishing number of insects have evolved disguises to evade crows, chipmunks and the rest. There are moths, beetles and several species of flies that mimic wasps in shape, colour and even sound.
To know whether a similar kind of disguise is involved in the red-eyed vireo's choice of wasp-nest paper for its home decoration, Heinrich devises an experiment that requires the acquisition of wasps' nests. The point is to determine whether the vireo's household adornment is sufficient to blunt the crows' desire for wasp grubs, or whether the presence of furious wasps is necessary to keep them away. Slapstick ensues.
Heinrich is an emeritus professor of biology at the University of Vermont, but he's also a famously obsessive, record-breaking marathon runner. His sprinting skills come in handy here. After a surfeit of wasp stings and a series of trials, one of which requires a five-hour drive from Maine back to Vermont with a huge wasp nest in the back of his pickup truck, Heinrich is ultimately confounded. But he's confident enough to propose that the red-eyed vireo's nest adornment habit is vestigial, like the human appendix.
Tossing an onion into the mixture for linseed oil comes from the time before thermometers, when an onion was handy to gauge temperature, but the custom persists, like serving only white wine with fish. The same kind of thing might be going on when the red-eyed vireo festoons its home with wasp-nest paper.
Summer, for Heinrich's purposes, is simply that part of the year in which sunlight and warmth sustain active life. By this measure, summer is roughly six months long, at temperate latitudes, with an average of 14 hours of sunlight a day. In the Vermont woods, it all begins with the return of the birds. Suddenly everything is blooming and croaking. It makes Heinrich go a bit crazy.
To be fair, it drives most of us a bit crazy, but in Heinrich's case the "summer awakening" sets him to furious note-taking and he finds it hard to sit still. "But I had to do it while I was still reasonably coherent, before the greening onslaught could rush in, and while the impressions were still fresh in my mind."
Then comes the hooting of owls. While summer causes most people to slack off, for most owls, it's all hard work. Rearing young takes the whole six months, with nest-building, egg incubation, feeding and training the youngsters in the arts of hunting. It's all about getting ready for winter.
Odd as it seems, for most trees it's about getting ready for the following summer. Trees routinely take nine months to prepare, beginning in midsummer, enclosing embryonic shoots, leaves and flowers in buds, in advance of the following spring. Wood frogs, meanwhile, spend more time than that doing absolutely nothing.
A wood frog will sit dead still under a leaf for nine months, most of the time frozen solid, with no breathing, heartbeat or brain activity. Then, on a single summer night, as if by magic, a pond will fill with thousands of them, and they will sing in a deafening chorus. That one night is when almost all the mating and egg-laying happens.
Once that's over with - Heinrich does not spare the reader any of the gruesome details of frog sex - the frogs retreat to pool edges and puddles, rarely if ever returning to open water. Most of them die before winter returns. It all seems so pointless. To Heinrich, it demands answers. Is the wood frogs' egg clumping advantageous for incubation and hurrying along the hatch?
Off we go with Heinrich on night-time expeditions to beaver ponds for more experiments, and he is only slightly disappointed to learn that for all his effort, his questions have been answered already, by scientists from Cornell University. Yes, egg-clustering is all about incubation and heat regulation.
Heinrich is undeterred, frog-wise - he once spent a summer keeping meticulous notes on the goings-on in 24 frog pools near his home - and he proceeds with his observations to a tentative hypothesis that raises questions about competition and co-operation as survival strategies.
It seems that the frog chorus is a collective effort to attract females to a pond, with little value to an individual male frog's competitive advantage. It seems also that the wood frogs' apparent overproduction of tadpoles is really an aid to group survival, by facilitating cannibalism when food gets scarce at summer's end.
Summer is upon us. Enjoy it while it lasts.
Terry Glavin is a journalist and author. His most recent book is Waiting for the Macaws: And Other Stories from the Age of Extinctions