Using data on 77 North American migratory bird species from the eBird citizen-science program, scientists at the Cornell Lab of Ornithology say that, in as little as four decades, it may be very difficult to predict how climate change will affect migratory bird populations and the ecosystems they inhabit.

Their conclusions are presented in a paper published in the journal Ecography.

Cornell Lab scientists generated new climate models incorporating multiple sources of data. This produced a timeline indicating when and where migratory bird populations are likely to be significantly affected by novel climates during each phase of their annual life cycles. It’s not that far off:

– Last 40 to 50 years of this century. During this period, migrants such as the Black-and-white Warbler are likely to first experience novel climates on their tropical wintering grounds (regions south of Florida) and also during the late summer on their breeding grounds in the North American temperate zone (above the nation’s midsection).

– First 50 years of the next century. This is when novel climates are likely to emerge for birds that winter in the subtropics — the southern half of the U.S.

The study authors conclude that by the middle of the next century migratory bird populations will experience novel climates during all phases of their annual life cycles. Frank La Sorte and co-authors considered minimum and maximum temperatures, and precipitation in the Western Hemisphere, week by week, for 280 years, from 2021 through 2300, under the worst-case scenario: continued high levels of greenhouse gas emissions. La Sorte says this is the first study to use a combination of climate variables to estimate when novel climates will first emerge, and it is the first study to examine the full annual cycle implications for a large number of migratory bird species.

The three data sources used for the study were 13 years of observations from the eBird program (2004-2016), climate projections from the most recent International Panel on Climate Change report, and NOAA data used to estimate climatic variation over a 60-year period. What constitutes a “novel” climate will depend on each region’s historical norms for that season.

This research was funded by The Leon Levy Foundation, The Wolf Creek Charitable Foundation, NASA, a MIcrosoft Azure Research Award, and the National Science Foundation.

Photos, from above: Black-and-white Warbler and Yellow Warbler by Kelly Colgan Azar.