Fall 2016

[News]

West Nile’s Impact on Birds Worse than Thought

Wildlife Professor Emeritus T. Luke George demonstrates bird banding techniques to students at the Wright Wildlife Refuge in Eureka.

IN THE FIRST IN-DEPTH STUDY of the West Nile virus’ impacts on bird populations, Wildlife Professor Emeritus T. Luke George, Washington University researcher Joe LaManna (’10, Natural Resources), and researchers from UCLA and the Institute for Bird Populations discovered the disease actually killed millions of birds—many more than previously thought. And it had a major, and sometimes lasting, impact on bird populations.

The virus affected nearly half of 49 bird species they examined at 500 sites across North America from 1992 to 2007. Some of the species rebounded, but others didn’t. For instance, an estimated 30 million of 130 million red-eyed vireos may have died from the virus, but their population recovered.

That wasn’t the case for warbling vireos. Their survival rate didn’t just drop with the arrival of the West Nile virus, but it stayed low. Over a five-year period, an estimated 15 million of the 49 million warbling vireos in North America died from the virus.

The study also revealed a long-term decline in survival for the Swainson’s thrush, a songbird commonly found in Humboldt County, a surprise given the virus wasn’t prevalent locally.

“Survival that is reduced and remains low for many years potentially has a long-term effect on bird populations locally, regionally, and across their range,” George says.
IN THE FIRST IN-DEPTH STUDY of the West Nile virus’ impacts on bird populations, Wildlife Professor Emeritus T. Luke George, Washington University researcher Joe LaManna (’10, Natural Resources), and researchers from UCLA and the Institute for Bird Populations discovered the disease actually killed millions of birds—many more than previously thought. And it had a major, and sometimes lasting, impact on bird populations.

The virus affected nearly half of 49 bird species they examined at 500 sites across North America from 1992 to 2007. Some of the species rebounded, but others didn’t. For instance, an estimated 30 million of 130 million red-eyed vireos may have died from the virus, but their population recovered.

That wasn’t the case for warbling vireos. Their survival rate didn’t just drop with the arrival of the West Nile virus, but it stayed low. Over a five-year period, an estimated 15 million of the 49 million warbling vireos in North America died from the virus.

The study also revealed a long-term decline in survival for the Swainson’s thrush, a songbird commonly found in Humboldt County, a surprise given the virus wasn’t prevalent locally.

“Survival that is reduced and remains low for many years potentially has a long-term effect on bird populations locally, regionally, and across their range,” George says.