The color of winter, of course, is white, as in snow. Writer/photographer/biologist Chadwick spent seven years--several of them with his then-wife--in pursuit of the elusive mountain goat, Oreamnos americanus, of western Montana. His fervent, distinctly first-person account of his fieldwork constitutes an authoritative description of a remarkable animal whose very existence was long doubted. Reasonably doubted, says Chadwick. Consider, after all, the likelihood of any creature enduring the 50Â°-below gales of a Rocky Mountain winter, or surviving a childhood on high, narrow ledges where certain death is the reward for ""any misstep, one foot failing to hold on an icy glaze or wet moss or crumbling rock."" Successive chapters focus systematically on: birth and the mother-kid relationship; evolution; social structure; mating; etc. Vivid observations of the goats' life and behavior are interlarded with brief lessons in ecology, physics, meteorology, field methods, and mechanics--all handled with easy erudition and a nice sense of their relevance. Throughout, Chadwick also finds occasion to report on other aspects of the mountain environment (including such associated species as wolverine, cutthroat trout, grizzly bears, and ticks). At one point, he stumbles into the midst of goat society. Taking notes on a nanny during the spring rutting season, he found himself being gored and knocked to the ground by ""the biggest billy I have ever seen."" Thereafter, ""Like other herd members. . . I was careful to give him a wide right-of-way when our paths crossed, respecting his private sphere of influence with the sincerity of a lower-ranking animal."" The final chapter sounds the ritual clarion for protection and ecological thoughtfulness--but not much less convincing for that. Solidly and agreeably informative.