Hummingbirds are fascinating creatures. They live only in the Western Hemisphere, with most of the approximately 340 species found in South America. Fifty-seven species live in North America; of these, 16 are migratory and breed in the U.S. They feed on nectar from flowers (and sugar water from feeders), which supply sucrose for energy. They also eat spiders and small insects, which provide protein for growth and reproduction. Some species may travel close to 4,000 miles during annual migrations from winter ranges in Central America to breeding areas in the Northwestern U.S. and Canada. A few even fly as far north as Alaska. They are the principal pollinator for 130 plant species, mostly wildflowers, in the Western U.S. Despite their tiny size, they play a vital role in the region's food chain -- one reason why it's important for officials to consider their needs when making land-management decisions.

The Hummingbird Monitoring Network is housed at the home of Susan Wethington and Lee Rogers in the Patagonia Mountains of southeastern Arizona. A tall woman with shoulder-length silvery hair and clear blue eyes, Wethington serves as the executive director and does it all -- fundraising, recruiting, training, monitoring, outreach. Before embarking on this mission, Wethington was an engineer with IBM, but she became fascinated by plants and birds during the four years she spent volunteering for the Arizona Sonoran Desert Museum in Tucson. By 1990, she was ready for a change. After applying for and receiving an educational leave from IBM, Wethington enrolled in the graduate program of the Department of Ecology and Evolutionary Biology at the University of Arizona. Her home was located in the path of migrating hummingbirds, so it seemed natural for her to focus on the little visitors. In 2000, she completed a Ph.D. on the interaction between hummingbirds and the plants they pollinate.

During her graduate work, Wethington realized how little was known about the population dynamics of hummingbirds in North America, even though their physiology had been fairly well studied. Determining the status of hummingbird populations is next to impossible without baseline information on each species, the habitat important to their survival, and the specific factors that threaten them. Even if it were determined that hummingbird populations were at risk and needed federal protection, no species can be listed under the Endangered Species Act without solid data.

To address this "hole in hummingbird conservation," Wethington sought out George West, a retired ornithologist from the University of Alaska who now lives in Green Valley, Ariz., and Barbara Carlson, then the director of nature reserves for the University of California-Riverside. Both were already active in hummingbird banding. In 2002, the trio founded the Hummingbird Monitoring Network.

They agreed from the start that the network would focus on setting up and running monitoring stations to collect data. That meant training and maintaining a small army of volunteers. In 2010, 1,500 retirees, college students, policemen, accountants and business owners monitored 32 sites across Arizona, California, British Columbia, Utah and Colorado. They donated 14,000 hours and drove 48,000 miles. The Hummingbird Monitoring Network runs on a shoestring: Its expenses were just $66,617 in 2010, with funding coming from government agencies, private individuals and foundations.

"You can get a tremendous amount of data collected for a limited amount of resources," says West. "And the volunteers get the satisfaction of knowing that they're gathering information that will eventually end up protecting and preserving hummingbird populations." Citizen scientists are also more likely to weigh in on policy decisions about natural resources. "Polls say that 85 percent of the American public support conservation," West adds. "Citizen science helps to energize some of that base."

There are potential disadvantages, though, and one of them is attrition. Volunteers tend to get bored and move on to other activities. Fortunately, that doesn't seem to be a big problem for HMN. "Hummingbirds are truly unique," says Sarah Haas, biologist for Bryce Canyon National Park in southern Utah, "the way they fly, their association with flowers, their ability to convey personality in such a small package." For Jane Pedersen at the Mesa Verde site, it's all about migration. "To know that these tiny birds that weigh just a few grams fly as far north as Alaska and back to the same spot here at the park year after year is just incredible!" Her voice rises with excitement. "Yesterday, I was watching a rufous sitting in a tree outside my bedroom window, and a wasp flew up, and he ate it. I thought, 'Oh, my goodness!' I knew they ate bugs, but I didn't think this tiny little hummingbird could take a bug that large."