Findings by UMass-Amherst led team uncovers critical effects of weather-induced mass mortality events on seemingly healthy populations

March 6, 2026

Thousands of birds, including beloved purple martins, died in “The Great Texas Freeze” of 2021. Thanks to a recent study published in Nature Ecology and Evolution led by biologists at the University of Massachusetts Amherst, we now know not only the extent of the die-off—up to 27% of the birds’ breeding population in Texas and Louisiana—but that recovery may take decades, and that we can expect weather-driven mass mortality events, increasingly common in the era of global climate change, may increasingly wreak havoc on animal populations.

For nine days in February 2021, two back-to-back deep-freezes gripped the Gulf Coast, dropping large loads of snow, sending temperatures plummeting, knocking out the Texas power grid and earning the nickname “The Great Texas Freeze.” It also resulted in the death of thousands of purple martins, a beloved migratory bird that annually arrives from its South American wintering grounds to the Gulf Coast in early February, just as the temperatures dropped.

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Stager and her co-authors worked with the Purple Martin Conservation Association (PMCA), which was founded almost 40 years ago and has members across North America; and Louisiana State University’s Museum of Natural History, which has one of the world’s preeminent collections of birds from the southeastern U.S., to create a baseline historical scenario against which deaths associated with the Great Freeze could be compared.

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Furthermore, the effects continued to be felt long after the storm. During the 2022 migration season, martins arrived at their breeding grounds two weeks later than normal, and they differed genetically from those that had died the year before—in some ways, they were more like individuals from martin populations found further north.

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