Proceedings Of The Third Expert Consultation Meeting On Bald Eagles In The Great Lakes Basin

`Are the Great Lakes getting better or worse?' This is the question that the public, scientists and managers are asking the International Joint Commission after a quarter-century of cooperative action by the United States and Canadian governments to clean up the Great Lakes. This volume contains papers from the workshop on Environmental Results, hosted in Windsor, Ontario, by the Great Lakes Science Advisory Board of the International Joint Commission, on September 12 and 13, 1996. The Great Lakes have been through almost a century of severe pollution from the manufacture, use and disposal of chemicals. In the 1960s wildlife biologists started to investigate the outbreaks of reproductive failure in fish-eating birds and ranch mink and to link these to exposure to organochlorine compounds. Human health researchers in the 1980s and 1990s linked growth retardation, behavioral anomalies and deficits in cognitive development with maternal consumption of Great Lakes fish prior to pregnancy. The Great Lakes became the laboratory where the theory of endocrine disruptors was first formulated. Now a group of Great Lakes scientists, hosted by the International Joint Commission, has compiled the story of the trends in the concentrations and effects of persistent toxic substances on wildlife and humans. The technical papers review the suitability of various organisms as indicators, and present the results of long-term monitoring of the concentrations and of the incidence of effects. The evidence shows that there was an enormous improvement in the late 1970s, but that in the late 1990s there are still concentrations of some persistent toxic substances that have stubbornly remained at levels that continue to cause toxicological effects.

Bayesian inference facilitated structured interpretation of a nonreplicated, experience-based survey of potential nesting habitat for bald eagles (Haliaeetus leucocephalus) along the five Great Lakes shorelines. We developed a pattern recognition (PATREC) model of our aerial search image with six habitat attributes: (a) tree cover, (b) proximity and (c) type/amount of human disturbance, (d) potential foraging habitat/shoreline irregularity, and suitable trees for (e) perching and (f) nesting. Tree cover greater than 10 percent, human disturbance more than 0.8 km away, a ratio of total to linear shoreline distance greater than 2.0, and suitable perch and nest trees were prerequisite for good eagle habitat (having sufficient physical attributes for bald eagle nesting). The estimated probability of good habitat was high (96 percent) when all attributes were optimal, and nonexistent (0 percent) when none of the model attributes were present. Of the 117 active bald eagle nests along the Great Lakes shorelines in 1992, 82 percent were in habitat classified as good. While our PATREC model provides a method for consistent interpretation of subjective surveyor experience, it also facilitates future management of bald eagle nesting habitat along Great Lakes shorelines by providing insight into the number, type, and relative importance of key habitat attributes. This practical application of Bayesian inference demonstrates the technique's advantages for effectively incorporating available expertise, detailing model development processes, enabling exploratory simulations, and facilitating long-term ecosystem monitoring.