Read an Excerpt
Summer World
A Season of Bounty
Chapter One
Preparing for Summer
9 March 2006. the ground is still snow-covered, but I've smelled the first skunk, and the bog is threaded by mink and otter tracks. I've heard the first honking of Canada geese. Two big flocks flew over, very high, heading north. The plant life looks unchanged, except that some pussy-willow buds have recently started to show a little more white peeking out over the edges of their dark brown flower bud scales. The first snowdrops, in the pure, unassuming simplicity that I love, are poking their nodding flower heads through the snow. Yesterday evening I heard the first singing of a mourning dove. The first robin is back, long before a worm is in sight. It's overcast and the forecast says "rain," but even if snow were predicted I'd expect the male red-winged blackbirds to return any day now.
Spring is on the way, and I think the birds feel it too. Certainly the blue jays do. I was lucky to see their first convocation again this year. I first noticed a crowd of them making a racket at seven am on the top of the bare branches of an ash tree—the same one where I saw them about this time last year. I counted at least twenty-four, but these jays were coming and going, so maybe there were many more. Those in the top of the tree were bobbing up and down in what looked like energetic knee-bend exercises, and calling at the same time. It did not look as though they were directing their attention in any particular direction or to specific individuals. There were no apparent pairs. I heard at least six to eight different calls, and each of these was given by the whole crowd during any oneperiod of time; they kept "in tune" as the calls changed. I was mesmerized and watched their display for three hours. The top of the one large ash tree seemed to be their stage, the focal point of a dance that extended over a dozen acres. At times there were groups of birds leaving the tree and screaming. They flew in twos and threes and in groups of a dozen or more. Whenever they went—using slow, deliberate wing beats—to or from their main staging area, they changed to a different vocalization. Although the main aggregation broke up at nearly eight am, a few pairs and individuals stayed around at least another two hours. They registered something that anticipates summer, and I assume their "dance" has something to do with courting and pairing up. Six weeks later, two pairs were still in the vicinity. I saw them busily coming to the edge of my recently dug frog pond to pull rootlets out of the ground for lining their nests.
summer in the northern hemisphere is short, and preparation for it is long. Getting an early start in the race to reproduce is critical. The season is anticipated by most organisms through photoperiod, the relative hours of day versus night. The seasons can also potentially be read from the stars. During summer, fall, winter, and spring in the northern hemisphere the North or "Pole" Star, Polaris, is visible as a steady fixed point above the horizon. Its angle to the Earth used to indicate latitude to the mariner. Daily, the constellations turn once around this star, rising in the east and setting in the west. Nearest to it we see the Big Dipper and Little Dipper and Cassiopeia. All three constellations are visible throughout the year, although in winter, when the tilt of the Earth's northern hemisphere is away from the sun, a new direction of the sky that was blocked during summer comes into view, with other constellations. Now the constellation Orion rises on the eastern horizon in the evening and dominates the southern sky, along with Sirius, a large star. During the summer in the northern hemisphere these winter stars are below the horizon, and the overhead sky is dominated by the Milky Way and three brilliant stars: Vega, Deneb, and Altair, of the constellations Lyra, Cygnus, and Aquila. Together these three stars, the "summer triangle," are a clear sign of summer. Do the birds know this?
Whether or not any animals can read and interpret the changing seasons from star patterns, and from them anticipate and prepare for the seasons, is not known. We do know, though, that animals use star patterns for navigation during their migrations. Many birds migrate at night, mainly the small songbirds whose rate of energy expenditure is so great that they need the day to refuel more often than large birds do. They watch the stars and recognize the patterns of the night sky. We know from detailed experiments and observations that they orient to the North Star or, more likely (as we do), by the star patterns around it, such as the Big Dipper. On their northward migrations to their summer breeding grounds they fly toward the Big Dipper, just as slaves escaping north at night followed it, code-naming it the "Drinking Gourd." When the birds return at the end of the summer, Polaris and the Big Dipper are on their backs or shoulders as they fly through the night sky.
Proximally, summer in the northern hemisphere is best defined, as already mentioned, by the period of sunlight and warmth that sustains active life. In the tropics "summer" is essentially endless; there are about 4,320 hours of daylight per year. Here in New England daylight is restricted to about 2,520 hours. And despite the much longer days in the arctic summer, there are fewer of them—not quite half those in New England. However, my calculation is an approximation only. I have for simplicity assumed (1) thirty-day months, (2) twelve months of summer with twelve hours of daylight per day in the tropics, (3) six months of summer with an average of fourteen hours of daylight per day in the temperate zone, and (4) two months of summer with twenty-four hours of light per day in the high arctic.
Summer World
A Season of Bounty. Copyright (c) by Bernd Heinrich . Reprinted by permission of HarperCollins Publishers, Inc. All rights reserved. Available now wherever books are sold.
