Is there a living Ivory-billed Woodpecker anywhere? There hasn't been a well-documented sighting since 1987, yet it still hasn't officially been declared extinct, giving hope to countless birders that they might yet spot this large, striking bird.

And yet...the probability that there are a few of the majestic woodpeckers that would spur viewers to declare, "Lord God, look at that bird!" is highly unlikely, note the authors of Facing Extinction: The World's Rarest Birds And The Race To Save Them. But officially declaring the Ivory-billed Woodpecker, which once was common in landscapes now devoted to places such as Big Thicket National Preserve in Texas, Congaree National Park in South Carolina, and Everglades National Park in Florida is something difficult, if not impossible, to do, they add.

With a home range that once covered roughly 186,000 square miles, a territory that does not include habitat in Cuba, performing the requisite, scientifically defensible survey needed to either spot the bird or declare it gone, would be mind-boggling to accomplish.

"Proof of extinction in this case is simply not feasible, and the best that can be done is establish the highest degree of probability of extinction; in spite of the considerable search effort so far expended on the Ivory-bill, the verdict (for the USA, but doubtless equally applicable to Cuba), is that it is too little, but not yet too late," they write.

And yet, they noted, "(T)he Ivory-billed Woodpecker of the USA and Cuba stays (listed as missing, not extinct) as long as it remains, as for the time being, one of the most sought-after species on the planet."

A collaboration of Paul F. Donald, Nigel J. Collar, Stuart J. Mardsden and Deborah J. Pain, Facing Extinction presents details on the status of this woodpecker along with 19 other case histories of some of the rarest birds in the world, according to the authors, and their ongoing fate. The book, now in its second edition, is a fascinating addition to any dedicated birder's library, yet also holds interest and intrique for the neophyte whose interest is piqued by what shows up at the backyard feeder.

What's the rarest bird in the world? A tough call, but the authors point to the Madagascar Pochard as a likely candidate, as there were fewer than 20 individuals alive in 2009, and just six were females. Another candidate would be the Sulu Hornbill, which might be represented by fewer than 20 pairs confined to an island in the Phillippines.

"It remains entirely possible, of course, that the world's rarest species is one that is not even known to science. When populations reach such low levels, even small changes in their numbers mean that the world's rarest species is likely to change frequently; the death of a single bird or a single successful nesting attempt might be sufficient to relegate or promote a species from this unfortunate status," they write. "For nearly a fifth of all bird species listed as Critically Endangered (the Ivory-billed is one), the most pressing question is not about how many birds there are, but whether the species still exists at all."

Along with the case studies, the authors go into the significance of rare species (for one, efforts to recover their populations can have far-ranging positive consequences), "hotspots" of rare species ("...islands hold a very high proportion of the world's rarest and most threatened birds, and were home to an overwhelming majority of species that have become extinct in the last 500 years"), and, of course, threats to the rarest species ("agriculture, habitat loss, and fragmentation").

There also is a chapter on how to save the world's rarest birds (captive breeding is one approach, improving, and even creating, habitat is another). In discussing this topic, the authors raise an eyebrow over U.S. efforts, or the lack thereof, to recover species, notably in Hawai'i.

"Clearly, the problems faced by Hawaiian birds are many and severe, and yet species have been successfully restored from tiny populations in the face of overwhelming odds elsewhere," they note. "New Zealand and the Mauritius have pioneered the restoration of relict and seemingly doomed populations. The failure of the world's wealthiest nation, where one person in five claims to be a birdwatcher, to prevent the recent extinctions in Hawaii begs an explanation."

Facing Extinction is a book rich in material concerning the plight of avian extinctions and how they can be slowed, if not reversed. It's a good addition to the research section of any birder's private library.