sources

JERALD J. DOSCH
ON DEAD BIRDS' TALES: MUSEUM SPECIMEN FEATHERS AS HISTORICAL ARCHIVES OF ENVIRONMENTAL POLLUTANTS

THE STUFFY AND LITERALLY stuffed old birds found in museum collections around the globe have tales to tell. Locked in the leg tags and plumages of these preserved specimens are historical environmental records of when and where their feathers were grown, what the birds were eating at the time, and what levels of certain environmental toxins were present in the habitat in which they were living. By combining information from avian study skins with historical maps and industrial records it may now be possible to determine both the sources and sinks of certain environmental pollutants over time.	1
Humans have long used birds as indicators of local environmental health. The proverbial "canary in a coal mine" was a live, caged bird that miners carried with them deep underground. The unique, highly efficient and sensitive respiratory system of birds makes them very receptive to atmospheric conditions. Thus, if miners saw their caged bird die they knew hazardous carbon monoxide or methane gas levels had reached dangerous concentrations in the air and it was time to flee the mine.1 In 1962, Rachel Carson's Silent Spring used birds to highlight the environmental dangers of pesticides.2 That same decade other scientists used over seventeen-hundred eggs from museums and personal collections to demonstrate the link between the decline in several species of fish-eating birds, the thinning of their egg shells, and chlorinated hydrocarbon insecticides such as DDT and its metabolite DDE.3 More recently, scientists have begun using stable-carbon, nitrogen, and other isotope ratios in feathers and eggs to reconstruct the diets and movement patterns of birds.4 As biological archives, feathers also can be used to reconstruct environmental toxin levels decades or even centuries into the past.	2
Figure 1. Common Loons Photo courtesy of the author. These birds at the University of Minnesota's Bell Museum of Natural History have been collected and preserved since the late nineteenth century.
Scientists began measuring the levels of heavy metals in bird feathers during the mid-1960s.5 Like the egg collections used to study the detrimental effects of DDT on avian reproduction, feathers from museum specimens also were used to track environmental pollutants through time. For example, a seminal 1966 paper using avian specimens from the Swedish Museum of Natural History documented fairly constant levels of mercury in Swedish birds collected from approximately 1840 to 1940; however, this was followed by a ten- to twentyfold increase during the 1940s and 1950s, likely due to the 1938–1940 introduction of alkyl-mercury compounds used to prevent fungal growth on seeds.6 As a result of this research, mercury-based seed dressings were banned in Sweden and later research once again used feathers to document the subsequent decline of mercury in birds.7	. . .