There are Three Billion Fewer Birds in North America Than 50 Years Ago

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Species of plants and animals are declining around the world; whether as a product of Earth’s cycles or mankind’s environmental interventions. As we record the lives and deaths of the species around us, scientists are still working to put together the pieces in time to save other living beings from being extinguished forever.

Scientists have noticed a steep decrease in bird species that can be found in North America. Common and rare birds are both experiencing population declines around the continent. Bird species that are becoming extinct or rare include snowy owls, sanderlings, cactus wrens, and Western meadowlarks, alongside many others.

Avian Population Decline

There are an estimated 3 million fewer birds in North America today than there were in 1970, according to recent research. Data was gathered using information gathered annually by citizen scientists in Canada and the United States, as well as radar used to track migratory bird populations. 

Scientists point to a few factors that could contribute to the loss of birds in this area of the world, including loss of habitat and human intervention. Some populations of birds couldn’t adapt to the increase of people and domesticated pets in their natural habitats, and weren’t able to find another suitable place to live before their populations began dropping.

Rather than focus on the loss of avian species in general, bird studies have shown how individual birds have adapted (or not adapted) to their changing environments. Individual birds pollinate, disperse seeds, and control pests; if individuals stop doing this, both the proliferation of the birds and the sustainability of their environment changes. 

Analyzing Avian Data

Citizen scientists have been integral to the data analyzed by bird researchers. Yearly observations of bird populations taken from the US and Canada showed changes in the number of birds of different species seen. Over 529 avian species showed population level changes, making up 76% of the birds that are active in North America. 

Net population change in North American migratory birds grouped by non-breeding biome.  Figure:  Rosenberg et al., 2019.
Net population change in North American migratory birds grouped by non- breeding biome. Figure: Rosenberg et al., 2019.

Habitat and bird species are both experiencing losses, and migratory birds feel these changes more so than non-migratory bird species. Grassland bird species have seen 700 million individual birds lost since 1970. Researchers have postulated that common birds will come in to take over environments where rarer birds can no longer live; however, common birds have seen equal losses in number as have birds with more specialized environmental needs. 


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Some scientists dub this dramatic loss in bird species an ecological crisis. On the other hand, species of waterfowl such as mallard ducks and Canadian geese have seen an increase in their numbers across North America. Scientists estimate that this bucking of the general trend is because of a focus on habitat and conservation efforts, which hopefully will also be leveraged towards species currently in decline. 

References

Rosenberg, K. V., Dokter, A. M., Blancher, P. J., Sauer, J. R., Smith, A. C., Smith, P. A., … & Marra, P. P. (2019). Decline of the North American avifauna. Science366(6461), 120-124. DOI: 10.1126/science.aaw1313

Lambert, Jonathan. We’ve lost 3 million birds since 1970 in North America. 19 September, 2019. Retrieved from https://www.sciencenews.org/article/3-billion-birds-lost-since-1970-north-america

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