In my first year of graduate school, a friend gave me a copy of the just-published Bumblebee Economics (1979), Bernd Heinrichs first book. I was riveted. I read it cover to cover in one sitting and have reread it several times since. Much of the book concerned foraging, which I was studying (and still do), but what made the book so absorbing was its presentation. Heinrich mixed fingers-in-the-muck field biology and rigorous science into a gripping narrative with the rhythm and pacing of a good novel. He leavened it with amusing and insightful personal anecdotes, beautified it with illustrations by his own hand, and created such a clear sense of place that readers were transported to the bogs and forests of New England the way that readers of, say, William Faulkner visit Yoknapatawpha County. Importantly, and also like a good novel, the book was about more than is described by its title. It addressed bigger themes like why and how scientists do what they do and what this tells us about nature and about ourselves. In his 15 or so subsequent books, Heinrich has developed these trademark elements into a distinctive style and has become perhaps our foremost living natural history writer.
In this book, The Nesting Season: Cuckoos, Cuckolds, and the Invention of Monogamy, Heinrich uses this same approach to examine all facets of breeding and the breeding seasons of birds. In 11 chapters, he examines mating systems, the timing of breeding, nest construction, courtship, eggs, predators, parenting, and nest parasites. His descriptions come from personal experiences with the birds he knows so intimately from his New England home (e.g., Canada geese, wood peewees, wrens, woodpeckers, swallows, ravens) and regular excursions into the scientific literature to look at species further afield—sandpipers in the Arctic, penguins in the Antarctic, birds of paradise in New Guinea. He investigates a whole range of questions about the reproductive habits of birds, ranging from classics of ornithology such as why birds pair up to rear offspring to minutiae such as the exact materials orioles use to build their hanging nests—the former tracked down in the extensive (100-plus years) ornithological literature, the latter from nose-to-the-ground research on his farm.
The pairing-up habits of birds get special attention in The Nesting Season. Commonplace among birds but unusual among other animals, this feature of avian reproduction is more human-like than the reproductive habits of most mammals, even those to whom we humans are most closely related. Heinrich discusses “monogamy“ in all its variety (e.g., social, sexual) as an adaptation that boosts reproduction under particular natural conditions. Under these conditions, mechanisms that promote (the right flavor of) monogamy are favored by selection, much as different patterns of egg blotching or coloring or particular types of nests might enhance the survival of eggs.
Especially pertinent to avian biology, as it is to human biology, is the magnitude of the job of child rearing. Offspring must be fed, protected, and cared for—a task that in most birds and in humans is more easily carried out by two parents than one. This much is widely accepted, but Heinrich also runs the logic the other way, and here, the book makes a contribution to our thinking on this subject. If we can gain understanding of monogamy in humans by studying birds, should we not also be able to gain insight into birds from our knowledge of humans? For example, why wouldn't deep bonds of affection and attachment develop to aid the reproductive enterprise of avian partners, much as they do in humans? Heinrich argues that the nervous and endocrine systems that all animals inherited from their evolutionary ancestors function in much the same ways, using the same structures and chemicals; therefore, they might be expected to be able to induce the same emotional effects when they are called for by ecological conditions. In other words, shouldn't birds also fall in love?
Heinrich's speculations on these ideas have received a lot of press, especially with regard to the film March of the Penguins, but media reporting cannot really transmit the extent and elegance of his argument. Fully aware of the pitfalls of anthropomorphism, he explicitly argues against any implication that we humans ought to better emulate the familial devotion of penguin parents, just as we should not condemn, for example, egret nestlings for killing their siblings. Penguins are penguins, egrets are egrets, and humans are humans. An understanding of one can provide insight to the other, and in Heinrich's world, this understanding brings appreciation and awe, not judgment.
The Nesting Season is referenced throughout, and 21 pages of endnotes provide direction to the literature Heinrich has consulted, making the book useful for layman and professional alike. It will join all of the other Heinrich books on my shelf, and I expect that I will return to this book from time to time, rereading it for the pure pleasure, as I do Bumblebee Economics or good novels. A popular book on natural history that also makes a scientific contribution while ranking as great literature is a rare bird indeed.
