Birds make for a good indicator of ecological sustainability. As advanced mammals, their decline is evidence of ecosystem declines that will impact human populations as well. Human habitat is threatened as never before - from forest fragmentation, toxics, climate change, and water scarcity. As go the birds will go the humans.

North American birds on the decline | csmonitor.com

In a striking trend that spans North America's key ecosystem regions - grassland, shrubland, forest, wetland, and urban - almost a third of 654 bird species native to North America are in "statistically significant decline," according to a first-ever "State of the Birds" report unveiled last month by the Audubon Society.