There are 3 billion fewer birds in North American skies than there were in 1970, according to a new report published this month in the journal Science. That’s a 29 percent drop.
Scientists blame the decline on the destruction of habitat, the spread of industrial agriculture and widespread use of pesticides. Those pesticides kill insects that birds rely on for food and can disrupt their migration. Shorebirds, nesting in areas especially vulnerable to development and climate change, have declined by more than one-third since 1970.
Old-world and new-world sparrows, warblers, blackbirds and larks are the five species in steepest decline, according to the report.
The numbers add up to a dire warning, said Ken Rosenberg, the study’s lead author and senior scientist at the Cornell Lab of Ornithology.
“These bird losses are a strong signal that our human-altered landscapes are losing their ability to support bird life,” he said in a statement. “And that is an indicator of a coming collapse of the overall environment.”
The only bright spot in the report happens to be relevant to the Ridgefield National Wildlife Refuge, a hotspot for migrating birds and wintering waterfowl.
Wetland birds have recovered strongly since 1970 — especially waterfowl such as ducks, geese and swans. Ironically enough, that’s because of “waterfowl hunters who raised their voice … and saw to it that conservation programs and policies were put in place” such as the North American Wetlands Conservation Act of 1989, Rosenberg said.
“Refuges have played a critical role” in that recovery, said Chris Lapp, the Ridgefield refuge project leader. “Our role is to manage high-quality waterfowl habitat.”
Raptors and bald eagles have also rebounded, the study found, thanks to conservation legislation and banning of the pesticide DDT.