Deborah Cramer centers The Narrow Edge on two seemingly very disparate creatures: the red knot – a lithe bundle of avian energy – and the lumbering, earth-bound, prehistoric horseshoe crab. But these organisms, their interactions, their environments, and their history simply serve as an opportunity to explore issues of species adaptations, ecological crisis, and conservation efforts. Following the red knot's migratory route, Cramer traveled over 40,000 miles from Tierra del Fuego to the Arctic, exploring organisms, history, and habitat along the way. The reader shares with her the wonder of this tiny bird that can fly up to 4000 miles without rest, unerringly finding feeding grounds and breeding grounds a hemisphere apart. Cramer notes: “Our human politics may vary, our needs and desires may conflict, and our values may differ, but this bird unites us along the shore of two entire continents….”

As she follows the birds, Cramer both rejoices in the beauty of the very disparate habitats along their route – windswept Argentina to the tidewaters of the American Atlantic coast, and beyond – and mourns the many rapid biological changes seen along the way. The interconnections between the birds and their energy sources (and the loss of these resources) are a continuing theme. The numbers Cramer presents are astonishing: At each feeding stop, the birds need to increase their weight by 50–100%. To gain this weight, knots eat a variety of food sources, but they prefer the lipid-rich eggs of horseshoe crabs. A single knot, in order to gain the weight needed, must eat 400,000 eggs. The challenges to these interdependent creatures are myriad: habitat loss, climate change, and overharvesting are a few of the familiar threats. Among these is the bleeding of horseshoe crabs for the LAL toxin detector, which brings Cramer to fishermen's boats and high-tech research facilities at Mass General and the Marine Biological Laboratories.

The book's two greatest assets are Cramer's lyrical, almost poetic, writing and the fascinating depth and breadth of information. However, both these strengths are also weaknesses at times, as emotion, fact, and perspectives ranging from worldwide to microscopic all jostle for the reader's attention, and Cramer's lyrical prose occasionally struggles in the fact-laden paragraphs. This can make the book difficult to follow as Cramer jumps from place to place and organism to organism. In the end, however, The Narrow Edge is a powerful presentation of the answer to Cramer's own question: “Does losing one more bird matter?” As such, it is a valuable addition to works of ecology and environmentalism for both students and teachers. In her conclusion, Cramer quotes graduate student Maria Perez: “To hold a red knot and feel its beating heart is to feel the heartbeat of the Earth.” This is “an Earth we all share,” Cramer adds: “Their home is ours. We stand together, all of us, on the edge, facing a time fraught with challenge, filled with promise.”

ELIZABETH COWLES teaches freshman-level biology, biochemistry, and entomology at Eastern Connecticut State University. She has taught at the undergraduate and graduate college levels for over 20 years. Her interests include insect toxicology, protein characterization, and astrobiology. Cowles holds degrees in biology and biochemistry from Cornell University and Michigan State University. Her address is Department of Biology, ECSU, 83 Windham St., Willimantic, CT 06226; e-mail: cowlese@easternct.edu.