Bird Population Has Plunged in North America

Cheryl Sanders
September 20, 2019

Grassland birds have suffered a 53% decrease in their numbers, and more than a third of the shorebird population has been lost.

Normally, it's hard to track animal populations this way. Those broad declines may not be readily visible to the average bird watcher, but over decades of data the devastating trend becomes all too clear. The study combines nearly 50 years of data, including information collected by citizen scientists and weather radar data of migratory birds from 143 stations across North America. "We saw this tremendous net loss across the entire bird community", said an applied conservation scientist. "We really need to take action quickly".

For their study, which was published Thursday in Science, researchers examined a dozen databases covering decades of bird observations in the US and Canada.

Study lead author Kenneth Rosenberg, a Cornell University conservation scientist, says the thinning of the flocks is happening before our eyes but is so slow we don't often notice.

Most of the losses were not among rare species, but common ones across almost every bird family and all habitats. Birds living in forests also showed massive hits, with total losses of more than a billion birds.

Some 90% of the total loss came from just 12 bird families and 19 widespread bird species such as the dark-eyed junco, common grackle and house sparrows.

The data added up to a grim conclusion: Over almost half a century, bird populations in North America had experienced a steep decline.

More than 1 billion birds have been lost from all forest biomes.

The extreme loss matches a similar picture emerging around the globe.

What's stunning in these newest findings is the fact that broad population declines are being recorded across North American birds as a whole, in a trend not confined to any one species or ecological niche. The study did not analyze causes of the declines.

While climate change was not the major driver of the population plunge, it was likely to exacerbate existing threats to bird populations, Rosenberg said.

"These data are consistent with what we're seeing elsewhere ... showing massive declines, including insects and amphibians", said Peter Marra, study co-author and director of the Georgetown Environment Initiative at Georgetown University. "Can you imagine a world without birdsong?"

But the study also showed that some bird populations have bounced back after suffering previous declines. Waterfowl management policies including wetland protection and restoration enabled ducks and geese to thrive, they added. The banning of DDT has allowed raptors, like the Bald Eagle, to also improve.

Species that had been introduced in certain areas didn't fare well, either.

"These are important examples that show, when we choose to make changes and actively manage the threats birds face, we can positively impact bird populations", Rosenberg said. "But the crisis reaches far beyond our individual borders".

"We're at a point where we can reverse these declines", says Rosenberg.

"Every field you lose, you lose the birds from that field", he said.

The researchers also said their estimates include only breeding populations, so the loss could be greater.

The new report is not about the loss of species but the loss of "abundance". In addition, many shorebirds breed in Arctic regions rapidly warming due to climate change.

Birds are part of a well-functioning ecosystem.

The researchers documented a steep decline for migratory birds.

So what can be done? But there are other things people can do to help. "And there are fewer birds for us to experience".

"Each of us can make a difference with everyday actions that together can save the lives of millions of birds - actions like making windows safer for birds, keeping cats indoors, and protecting habitat", Parr said.

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