Magazine article Science News

... and the Big Bird That Didn't

Magazine article Science News

... and the Big Bird That Didn't

Article excerpt

Its varied diet may have permitted the California condor, one of today's largest and rarest birds, to survive the mass extinctions at the end of the last ice age, according to a new study. Many species of large land mammals died off about 12,000 years ago. Some scientists blame those extinctions on changes in climate, hunting by humans, virulent diseases, or a combination of those factors. Whatever the cause of the die-offs, they removed a considerable source of carcasses for scavengers. As a result, many scavengers suffered population crashes as well, says Kena Fox-Dobbs of the University of California, Santa Cruz.

California's La Brea tar pits became a tomb for many predators and scavengers, and scientists there have examined the creatures' remains to glean hints about ancient diets. Avian fossils excavated include California condors and representatives of other large extinct species such as the western black vulture (Coragyps occidentalis) and the teratorn (Teratornis merriami). The three types of scavengers seem to have been common in the region during the last ice age, but only the condors survived the post-ice age extinctions.

Nitrogen isotopes in collagen extracted from the fossil bones of the species provide important details about those birds' diets, says Fox-Dobbs. In particular, the ratio of nitrogen-15 and nitrogen-14 in bone collagen distinguishes predators and scavengers that consume grass-grazing herbivores from those that consume leaf-eating browsers. …

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