- The Washington Times - Monday, December 16, 2002

The world of wildlife habitat is getting smaller, which is not good for birds.
Of the 485 animal species that have become extinct since 1600, 116 of them, nearly a quarter, are birds. Of the 9,500 or so listed as threatened by the World Conservation Union's Red List in 2000, more than 2,100, more than a fifth, are birds.
The dodo and passenger pigeon are among the most famous examples. Others, such as the Guam flycatcher and Carolina parakeet, are relatively obscure. Some are having near-death experiences with varying degrees of recovery success. The California condor, bald eagle and whooping crane come to mind.
Aside from some plants, bird species are showing the worst survival record in the natural world.
The disaster rate may look higher because we know more about birds than we do about many other animals. People have been fascinated by birds for millennia and have tracked their biology closely. Bird-watchers are among the most avid and dedicated of conservationists, and among the best-informed.
Despite this interest, many bird species remain on the edge of oblivion, and increasing scientific evidence suggests that habitat fragmentation is the culprit. The longer people have lived in a given place, the more bird species sharing the locale become extinct.
A study last summer by U.S. Geological Survey biologist Rosalind Renfrew and colleagues from the University of Wisconsin found that the shrinking of North American grassland habitats were killing off bird species. Many grassland species nest in the open. If they do not have large open areas available, they have decreased nesting success because they are more vulnerable to predators.
Animals that prey on these birds' nests opossums, raccoons, squirrels and snakes prefer the woody edges of grassland. When the large areas are carved up, it creates more edges for predators to live.
Because these areas often are carved up for housing developments or shopping malls, the effect tends to favor predators that do well around people, such as raccoons, opossum and coyotes.
The scientists conclude that habitat fragmentation makes it easier for more predators to find the nests.
More bad news can be found in a study from Tom Brooks of the University of Arkansas, and Lisa Manne and Stuart Pimm of the University of Tennessee. Mr. Pimm is the godfather of bird-extinction studies. The trio found that, contrary to long-held beliefs, island bird species no longer may be more vulnerable to extinction than their continental counterparts.
"Historically," they said, "a higher proportion of species extinctions have occurred on islands rather than on continents. So scientists have assumed that island species are inherently more vulnerable to the threat of extinction." Ms. Mann, Mr. Brooks and Mr. Pimm found the opposite was true: "Lowland continental areas have a higher proportion of threatened bird species within similarly sized breeding ranges."
The group concluded, "The added and unexpected vulnerability of range-restricted lowland bird species gives conservation organizations and governmental organizations another priority: To proactively protect these ecosystems now, so bird species won't disappear later."
It is probably futile to suggest that human beings stop invading forests and prairies to save vulnerable bird species, but planning these invasions better to preserve preferred habitat for birds and other species may help their long-term survival.
The work of University of Colorado biologist Carl Bock indicates that the size and shape of open spaces may reduce the vulnerability of species. Development that leaves large prairielike open spaces, with a minimum of edge habitat to hide predators, may offer the best hope for lowland birds.
It now seems that every continent is an island.
Stuart Pimm told UPI, "The Oxford English Dictionary says of the dodo" a former resident of the island of Mauritius "that it 'went extinct,' as if it was the dodo's own stupid fault." In fact, Mr. Pimm said, the dodo met its fate at the hands of human beings, the same species that is shrinking the continents.


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