Scott Weidensaul, A World on the Wing **** 1/2

I expected this book about "The Global Odyssey of Migratory Birds" to focus primarily on the mysteries of avian navigation, something like We, The Navigators but for birds. However, it takes a far more expansive look at avian biology and ecology.

The author does a beautiful job of balancing between travelogue, science, and advocacy. He provides lovely natural descriptions of his birding expeditions:

The world was precisely equal halves of gray, divided by the flat line of the horizon––the smoky silver of an overcast sky, unmarked and smooth, and the darker, mottled granite and charcoal of a mudflat that stretched to every side, paper-thin sheets of water lying on its surface reflecting the clouds or ruffled by the breeze.

Clear explanations of biological marvels:

Migratory birds can grow and jettison their internal organs on an as-needed basis, bolster their flight performance by juicing on naturally occurring performance-enhancing drugs, and enjoy perfect health despite seasonally exhibiting all the signs of morbid obesity, diabetes, and looming heart disease. A migrating bird can put alternating halves of its brain to sleep while flying for days, weeks, or even months on end ... get[ting] mentally sharper under such conditions.

And practical illustrations of environmental activism:

Land managers knew that some ag[riculture] lands, like rice fields, can provide good habitat for waterbirds, provided they're flooded at the right time and to the proper depth. Looking at eBird data, they also realized that many migrants were only using the Central Valley for a few weeks... Farmers would be paid to keep a few inches of water in their fields in late summer and early autumn, when shorebirds are migrating south through the region.

I appreciated how the book showed interconnections between elements of the ecosystem, such as the so-called "carry-over effects" of conditions in the wintering grounds onto breeding season. Spring is coming earlier in the Arctic but celestial cues in the tropics are unchanged, resulting in birds arriving too late for the caterpillar boom; the fragmentation of forests results in more "edges" and therefore more predators like raccoons, skunks, and crows. I also appreciated that Weidensaul includes success stories to ameliorate the hopelessness of many works of conservational activism.