A biologist studying wild songbirds in New York State has found that all 178 woodland birds he tested last year had unusually high levels of mercury in their blood and feathers, a sign that the toxic chemical has spread farther in the environment than previously thought.

The biologist, David C. Evers, who is also executive director of the Biodiversity Research Institute, a nonprofit ecological organization in Gorham, Me., said that his preliminary findings challenged existing perceptions about how far mercury travels, how it interacts with the environment and how it affects various forms of wildlife — all with worrisome implications for people.

While mercury has often been found in lakes and streams and in fish, Dr. Evers’s work documents the unexpected presence of the chemical in birds that do not live on water and never eat fish.

“Impacts on biological diversity usually show impacts on human health,” Dr. Evers said in a telephone interview. “If these birds are having trouble, that should be a very good indicator of a risk to our own well-being and health as well.”