Wednesday, January 8, 2020

Bird Migration Timing Skewed by Climate Change

Results of a new study indicate the changing climate has affected the timing of spring migrations during the past two decades for many birds, including these migrating Ross’s Geese.

A study using weather radar data collected over the past quarter-century detected bird migration changes on a continental scale according to a team of researchers that revealed the timing of spring bird migration across North America is shifting as a result of climate change. The study found that spring migrants were likely to pass certain locations earlier now than they did 20 years ago. Temperature and migration timing were closely aligned, with the greatest changes in migration timing occurring in regions warming most rapidly due to climate change. Using 24 years of weather radar data, the study found that during fall, shifts in migration timing were less apparent.

The study is one of the first to examine the subject on a continental scale was conducted by scientists from Colorado State University, the Cornell Lab of Ornithology, and the University of Massachusetts – and was recently published in the journal Nature Climate Change.

“To see changes in timing at continental scales is truly impressive, especially considering the diversity of behaviors and strategies used by the hundreds of species of birds the radars record,” said lead author Kyle Horton, an assistant professor at Colorado State University.

Horton noted that the timing shift doesn't necessarily mean that the birds are keeping pace with climate change; and there’s concern about a mismatch between when birds arrive and when blooming plants and insects they need for food are at their peak abundance.

Andrew Farnsworth, co-author and researcher at the Cornell Lab of Ornithology, said the team’s research answers some key questions: "Bird migration evolved largely as a response to changing climate. It’s a global phenomenon involving billions of birds annually,” he explained. “It’s not a surprise that bird movements track changing climates, but how bird populations respond in an era of such rapid and extreme changes in climate has been a black box. Capturing scales and magnitudes of migration changes over time has been impossible until recently.”

The study authors found the lack of change in fall migration patterns surprising, but said migration also tends to be a “little bit messier” during late summer and fall months when there’s not the same pressure to reach wintering ranges, and migration tends to move at a slower pace.

What’s next? The researchers plan to expand their data analysis to include Alaska, where climate change is occurring faster and having more serious impacts than in the lower 48 states.

Publication Reference: Kyle Horton, Frank La Sorte, Daniel Sheldon, Tsung-Yu Lin, Kevin Winner, Garrett Bernstein, Subhransu Maji, Wesley Hochachka, Andrew Farnsworth. Phenology of Nocturnal Avian Migration has Shifted at the Continental Scale. Nature Climate Change 2019, which can be accessed at