Decline of the North American avifauna

Species extinctions have defined the global biodiversity crisis, but extinction begins with loss in abundance of organisms that can result in extreme compositional and functional changes of ecosystems. Using multiple and independent monitoring networks, we report major population losses across much of the North American avifauna, including in once common species and from nearly every biome. Integration of trend and population size estimates indicates a net loss approaching three billion birds, or 29% of 1970 abundance. Continent-wide weather radar also reveals a comparable decline in biomass passage of migrating birds over a recent 10-year period. Our estimates of abundance and biodiversity loss signals an urgent need to address ongoing threats, in order to avert future avifaunal collapse and associated loss of ecosystem integrity and function.