correlations in distributions), the potential interactions among stressor impacts, and the relative 
risks among potential stressors to populations of loons at various spatial scales. The research 
will secondarily characterize risks for the belted kingfisher {Ceryle alcyon\ another piscivorous 
bird that is often the focus of ecological risk assessments because its small body size and high 
food ingestion rate lead to estimates of high potential risk. 
To improve the process of developing risk-based criteria for mercury protective of loons and 
other piscivorous birds, advancements in model and method development and data acquisition 
are needed in five major areas. First, the landscape of interest needs to be characterized, 
including the spatial and temporal distribution of stressors and available habitat for species of 
interest Second, stressor-response relationships are needed, especially for endpoints related to 
survival and fecundity rates. Relationships may be developed empirically fi’om field data or 
generated in laboratory tests based on representative exposure scenarios. Third, methods for 
interspecies extrapolations of stressor-response relationships for mercury are needed. Fourth, 
age-class matrix population models incorporating stressor-response relationships are needed for 
loons and other piscivorous birds. Fifth, population dynamics need to be assessed across 
heterogeneous landscapes where variable stressor levels and habitat qualities influence the 
distribution of populations. Information from the five areas is connected through important 
feedback loops (e.g., knowledge of population dynamics captured in the matrix models also 
informs the selection of landscapes and endpoints for dose-response testing). Research on 
landscape characterization, population model development, and determining and extrapolating 
dose-response information will proceed in parallel. The level of refinanent needed in the models 
and acquired data is a function of the degree of uncertainty acceptable for setting criteria, so the 
application of tools will explicitly consider the availability and quality of data for various tiers of 
risk assessment. 
1. Landscape Characterization. 
A demonstration project on risks to loons would focus on landscapes in the upper Midwest and 
Northeastern United States. Characterization of these landscapes would include: 
• Collection of mercury residue distribution in fish and water bodies across the landscape. 
This would be based primarily on a synthesis of existing monitoring data from Federal, 
State, academic, and non-profit organization sources. 
• CharacterizaticMi of habitat quality for species of interest across the landscape. For lotxis, 
key habitat characteristics would include presence of suitable nesting and brood rearing 
sites, measures of human disturbance, density or extent of human dwellings and other 
activities around lakes, turbidity, and the availability of suitable forage fish supplies. 
This information would be synthesized from available monitoring databases and/or aerial 
photographs. 
• Collection of data on the abundance and distribution of loons and other piscivorous birds, 
and on juvenile production rates by location. This information would be based on long¬ 
term loon monitoring programs that exist in the upper Midwest and the Northeast. 
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