| Data from the Michigan Bald Eagle Biomonitoring Project (MBEBP) was used to provide ecological evaluations amidst concerns of emerging contaminants and environmental change. Samples and measurements were collected throughout the state of Michigan from 1998-2012. Nestling breast feathers and biometric measurements were used in analytical and statistical analyses which provided a broad assessment of the Great Lakes ecosystem and its resident bald eagles. Bald eagle nestling feathers were taken from Michigan breeding areas, and used to evaluate spatial and temporal trends of mercury (Hg). Overall, remediation has positively affected the Great Lakes region. However, Michigan's Upper Peninsula and Lake Superior shoreline had areas with consistently elevated Hg levels. Possible mechanisms causing increased Hg in these areas are localized coal consumption in addition to atmospheric inputs from the northwestern United States and Asia. This study also addressed concerns regarding nestlings that were exhibiting unusual behavior, morbidity, and/or direct or indirect mortality (i.e. dead sibling or addled egg present) by determining effects from metals/metalloids of concern. In addition to Hg, lead (Pb), cadmium (Cd) and arsenic (As) were measured in nestling feather samples. These metals, although ubiquitous in the environment, were not the primary cause of nestling bald eagle morbidity and mortality observed in the field. It is likely that the expanding population is either experiencing natural causes of mortality, or other mechanisms are causing stress on individual nestlings such as climate or food availability. Lastly, the study evaluated the bald eagle population's response to environmental change by analyzing productivity and biometric measurements of bald eagle nestlings' bill depth, culmen length, footpad, and hallux claw. The mechanisms acting upon body size clines are complex. There was a correlation between year and deceasing body measurements in nestling bald eagles; however, it is important to recognize that year encompasses several predictors such as food availability. It is likely that several factors are influencing measurements which create difficulties in modeling effects with statistical significance. However, it is notable that statistical significance was achieved in such a short period of time. The utility of the bald eagle as a sentinel species is apparent with the quantity and quality of spatial and temporal trend data that align with other intensive studies. As the Michigan bald eagle population grows and expands into new habitat, so does the capacity for it to provide new information about the environment. The MBEBP not only provides important information regarding the species, it continues to successfully monitor the health of the Great Lakes ecosystem. |
