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The Power of the Crowd

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by Sophie Brown
Photograph by Ted Schroeder

FeederWatch data yield insights on bird trends, invasive species, and disease

Since 1987, volunteers have been collecting data from more than 40,000 backyard bird feeders across North America for Project FeederWatch, a citizen-science project managed by the Cornell Lab of Ornithology and Bird Studies Canada. The spatial and temporal scope of the project is of great value in studying birds. Citizen Science director Janis Dickinson said, “The power of the crowd is amazing. Our scientists are thrilled to join with so many people working together to achieve common science and conservation goals.”

In a 2009 paper published in The Proceedings of the Fourth International Partners in Flight Conference, Cornell Lab scientists David Bonter and Wesley Hochachka discuss three cases in which FeederWatchers helped researchers track important trends: the decline of a common species, the spread of an invasive species, and the spread of new diseases.

FeederWatch data revealed a significant and widespread population decline in Evening Grosbeaks from 1988 to 2006. Participants during those 18 years reported a 27-percent decrease in flock size and sites with Evening Grosbeaks decreased by 50 percent. Although many people have noticed the lack of grosbeaks, FeederWatch provided a clear, data-driven picture of the magnitude and geographical scope of the decline.

FeederWatchers also helped scientists track the range expansion of Eurasian Collared-Doves, which were introduced to the Bahamas in the 1970s and spread through Florida and now much of North America.

In winter 1993–94, a strain of the bacterium Mycoplasma gallisepticum started infecting House Finches. FeederWatch participants were asked to note the numbers of apparently sick and healthy birds. Scientists developed the House Finch Disease Survey using the FeederWatch platform to investigate the dynamics of the disease. FeederWatch data have also been used to study population changes that may be associated with West Nile virus.

David Bonter and Wesley Hochachka note that it can be a mistake to ignore citizen-science opportunities to document effects of unexpected events. Between 1962 and 1974, participants in the U.K.’s Common Bird Census were specifically asked not to count House Sparrows because they were so ubiquitous and abundant. But in recent years, House Sparrow populations in the U.K. and Europe have declined precipitously—by more than 95 percent in some areas. Sadly, scientists lost the opportunity to gather information during the start of this unexpected decline.

In their 2009 paper, David and Wesley write, “Much of our knowledge of trends in the distribution and abundance of birds in North America has been generated from data gathered through public engagement in citizen-science programs.”

“The Cornell Lab has had the right vision,” said Janis Dickinson. “The contributions of citizen scientists, many of them highly skilled birders, are of profound importance to our research and conservation missions.”

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