"This report is based on the first-ever conservation vulnerability assessment for all 1,154 native bird species that occur in Canada, the continental United States, and Mexico. The assessment was compiled by a team of experts from all three countries. Of these 1,154 species, 432 qualified for the Watch List, indicating species of highest conservation concern based on high vulnerability scores across multiple factors."
Yes, extinction is natural. But the reason the background extinction rate is at least 1,000 times above normal is because of what we're doing to the planet.
Link: The Report (.PDF)