Review: The Nesting Season

Bernd Heinrich, The Belknap Press of Harvard University Press, 2010

 

We can’t help it. We come to terms with the world only through the lens of the rich self awareness that is unique to our species. We explain animal behavior by ascribing to them human motivation. We find monogamy to be an endearing trait in birds despite the fact that total sexual fidelity is rare even in our own species. And we ask “why?” Why do birds sit on eggs?  Why do some birds build elaborate nests which they take great pains to hide, while others deposit all their eggs in a totally exposed and seemingly perilous scrape in the ground? Why do some birds build their nests in or very near the nests of raptors which would see them as a snack but for the geography?

 

The sin of anthropomorphism is a forgivable one if we keep in mind that “why?” is a shorthand way of asking “what selection advantage is conferred by this behavior?” The answers to our whys are woven through the warp and weft of the myriad details of food supply, the availability of suitable habitat, predation, the precise timing of arrival on territory, and the extreme demands of parenting. Our endless whys have turned the study of mating behavior into the hottest topic in biology since Darwin, because continuation is the most pressing business for every species from the simple to the complicated.

 

Backyard bird watchers and academic ornithologists ask the same questions.  The difference is that professionals think of more of them. Why do birds sit on eggs when they cannot possibly know what an egg is?  (We know this because birds have contentedly incubated rocks, film containers, and other debris placed in their nests by curious graduate students as substitutes for real eggs.)  Since birds (presumably) cannot count they don’t know how many eggs they have, so why do they produce a replacement when an egg is removed from their nest.  Why do birds remove egg fragments from their nests after hatching if they don’t know what they are?  Given the extreme demands of bird parenting, a steadfast partner would seem to be a big advantage. So why aren’t all birds monogamous? Given that sperm is cheap and eggs expensive logic would point to polygyny as the best strategy for males to spread their genes, so why isn’t polygyny universal? Shouldn’t polyandry be the best strategy for females to gain parenting help from more than one male?  Why do some birds forgo parenting responsibilities by depositing their eggs in the nests of others and then stick around to punish adoptive parents who don’t fulfill the service into which they have been pressed?

The answers are in the details rather than logic, for if the world were a logical place men would ride sidesaddle. In the search for answers scientists inevitably reach the same conclusion as Woody Allen did in a recent film – that “whatever works” is the best explanation for all behavior. All strategies are fungible. Although much bird behavior is hard-wired, evolutionary forces ruthlessly select for those individuals in a population whose behavior succeeds in a given situation in the same way that they confer selection advantages on some morphological traits.

 

As Marcel Proust illuminated our understanding of the brain, memory, and the self through artfully obsessive attention to detail, Bernd Heinrich, in The Nesting Season, illuminates our understanding of mating behavior through a similar focus on those details of life which most of us never notice. Heinrich, the son of a compulsively curious biologist, grew up in the field collecting, hunting, looking at, drawing, and keeping journals of his experiences of birds and bugs. He earned academic credentials and taught biology at the University of Vermont, a position from which he is now retired. Fortunately for us, he is also a prolific writer whose previous books have explained bumblebee economics, long-distance running (he is an ultra-marathoner), winter survival strategies, nature in summer, and animal intelligence.

 

Professor Heinrich’s exploration of mating behavior in his newest book, The Nesting Season, begins with an anecdote about the demands of bird parenting in which he recounts losing an adopted goose chick to a raven:

 

Parenting is a good place to begin the exploration of mating behavior because its demands suggest answers to many of our questions about the advantages and disadvantages of various strategies. Monogamy, he explains, works in certain situations because the extreme demands of parenting require the cooperation of the male parent who can maximize his reproductive success only by forgoing mating opportunities with other females. But strategies involving multiple partners are more successful in other circumstances. Heinrich writes:

 

In other words: “whatever works.”

 

Heinrich’s writing is dense and chockablock full of questions, details, personal anecdotes, wit, and conclusions drawn from the author’s lifetime of observations in the field. Like his previous books, The Nesting Season illustrated with the author’s own drawings, watercolors, and photographs. Like his previous books, The Nesting Season is one to read and read again.

 

Wayne Mones

October 14, 2010