Many bird populations in trouble, report says

Just as they were when Rachel Carson published 'Silent Spring' nearly 50 years ago, birds today are a bellwether of the health of land, water and ecosystems.

From shorebirds in New England to warblers in Michigan to songbirds in Hawaii, we are seeing disturbing downward population trends that should set off environmental alarm bells.

The declines can be traced to a variety of factors, depending on a bird's particular habitat. But the causes most frequently cited in the report are agriculture, climate change, development and energy, and invasive species.

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