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Endangered Species 2011

Endangered Species 2011 - Endangered species Biodiversity 3...

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1 Biodiversity 3: Endangered species Endangered species Estimating risk of extinction Major causes of threat Protecting endangered species (Endangered Species Act) Passenger Pigeon Highly social birds Nested in forest colonies Abandoned chicks after 2 weeks “ The air was literally filled with Pigeons; the light of noon-day was obscured as by an eclipse, the dung fell in spots, not unlike melting flakes of snow; and the continued buzz of wings had a tendency to lull my senses to repose." - James J. Audubon 1813 Hunted to extinction • 1914: 1 bird left in Cincinnati Zoo • Uncontrolled hunting • 1855: 18,000 / day • Population collapsed in late 1800s “Martha” Why didn’t pigeons recover? • Breeding patterns required large social groups (predator defense) • Forest clearing (lack of nesting and feeding sites) Hunting drove pigeons close to extinction, but habitat loss and breakdown of social structure finished them off
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