One August many years ago, I joined a weeklong expedition to Michigan's thickly forested Isle Royale to help gather information about the local moose and wolves. Six of us volunteers, led by a biologist, bushwhacked all day through dense underbrush searching for moose antlers and bones. Whenever we found them, we took measurements, recorded more details, and stuffed samples into our packs for lab analysis. In the afternoons, we hiked to ridgetops and used a handheld antenna to listen for clicks from the radio collars worn by roaming wolves.

Our exhausting but enjoyable effort was part of a program run by the nonprofit Earthwatch, whose mission is "to engage people worldwide in scientific field research and education in order to promote the understanding and action necessary for a sustainable environment." We were assisting a study of predator-prey dynamics on the island that's been under way since 1958. Over the past two decades, more than 700 "citizen scientists" have gathered thousands of moose bones. "Most of what we know about the moose population comes from that systematic collection," says John Vucetich, co-leader of the study and associate professor of wildlife ecology at Michigan Technological University. From the collected bones, researchers can learn when a moose died, how old it was, and its physical condition prior to death. Carbon isotopes in the samples also reveal long-term changes in the vegetation moose eat. "Without all those volunteers," Vucetich says, "we'd have a much smaller sample size and less valid conclusions."

Citizen scientists are also gathering useful data about much tinier creatures -- hummingbirds. In this issue of HCN, writer Jean Palumbo tells us how volunteers around the West trap and band these miniature birds, gathering valuable information about their migrations, ranges and food sources. Hummer research is relatively young, but, like the wolf/moose study, it may reveal important patterns and long-term changes. Certainly, it will grow more valuable over time.

Such efforts help underfunded scientists in many ways. "Collecting data is expensive," says Vucetich, "and having volunteers defrays that cost." He notes that the best citizen science projects don't require a high level of skill, but are fascinating for the participants -- measuring water quality in the Colorado River, for example, or monitoring bald eagle nests in Arizona, or playing a computer game that optimizes sequences of human DNA (which helps biologists study genetic diseases). Public involvement presents challenges as well; volunteers must be trained to make reliable observations, and the scientific community sometimes needs encouragement to accept "non-expert" data.

But in an era when federal and state research projects have been cut back and the general public often knows dismayingly little about science, citizen scientists can become a small army of informed advocates. "Science belongs to the people," says Vucetich. "It's not just the facts that are discovered. It's the public's reaction to those facts, the dialogue. That's how policy gets made."