From the book jacket: "From flying squirrels to grizzly bears, and from torpid turtles to insects with antifreeze, the animal kingdom relies on some staggering evolutionary innovations to survive winter. Unlike their human counterparts, who must alter the environment to accommodate physical limitations, animals are adaptable to an amazing range of conditions. Examining everything from food sources in the extremely barren winter landscape to the chemical composition that allows certain creatures to survive, Heinrich's Winter World awakens the largely undiscovered mysteries by which nature sustains herself through winter's harsh, cruel exigencies."

REVIEWS (4 of 5 stars on Amazon): "Even those who limit their acquaintance with cold to the ski slopes will find in Winter World a book of wonders and delights." —San Diego Union-Tribune

"Heinrich has the rare ability to embed dense scientific explications within graceful, light-footed nature writing." —The New York Times Book Review


Ultrarunning performance premiums maximizing exercise performance in the context of fuel economy, and although the ultimate exercise capacities are achieved by some insects, we find it hard to identify with them. With birds, it is easier, and I have since a small boy identified with a tiny northern bird, the kinglet, as a marvel from its extraordinary performance of survival in winter. It is an insect-feeder that may stay all winter in the Maine woods, surviving temperatures down to -30 degrees F, while keeping its body temperature above freezing, likely at least near normal bird body temperature of near 105 degrees F. How does it manage its apparently massive rates of heat production, those required to keep such a tiny body warm? The bird defied the odds, because it is an insectivore. Where do the birds' calories come from since there are not many if any insects about in the north woods in the depths of winter?

I had some ideas but no knowledge of the golden-crowned kinglets' options, but I knew for sure was that it must require something more than just extra-ordinary exercise capacity sustained over very long durations.  It epitomized to me the problem of animals' winter survival, in both the constraints and possibilities in their utmost, as problems that have been solved through evolution in likely diverse ways. The topic concerned animal physiology and behavior, and was for many years core to my teaching a course I titled, “Physiological Ecology” at U.C. Berkeley in the entomology department where I confined it to insects. After moving to the University of Vermont's biology department, I included also the vertebrate animals. Here I later added a field component, titled "Winter Ecology," a special course where a small group of students and I stayed at my primitive cabin in the Maine woods during the winter semester break. Winter World was not necessarily meant as a textbook. It was aimed for a general readership for those interested in some of the amazing things animals do in the winter to survive.

On finishing writing the book I still didn’t know how kinglets managed to survive in the winter, but had arrived at what I thought would be a likely hypothesis. Being hyper-alert to it and these amazing birds from my writing about them, I later saw them in the act, and captured them in a photograph high in a tree in the middle of the night, that proved it. It was my luckiest ever, and still one of my most prized.