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Juvenile Survival in Common Loons Gavia Immer: Effects of Natal Lake Size and pH
Citation:
PIPER, W. H., J. S. GREAR, AND M. MEYER. Juvenile Survival in Common Loons Gavia Immer: Effects of Natal Lake Size and pH. Journal of Avian Biology. Wiley InterScience, Silver Spring, MD, 43(3):280-288, (2012).
Impact/Purpose:
This publication contributes to the demonstration and implementation of NHEERL’s Wildlife Research Strategy. That strategy describes methods by which population models will be used to integrate stressor impairments of multiple organismal-level endpoints (e.g., survival and reproduction) into a population-level assessment of ecological risk. Demonstration of this methodology currently focuses on the common loon (Gavia immer). To that end, a previous publication (Grear et al. 2009, J. of Wildl. Manage.) identified juvenile survival as an important data gap in the demonstration. Thus, through collaboration with state and non-government cooperators, this publication uses mark-recapture analysis of banded loons to estimate juvenile survival and its relationship to the pH of natal lake habitats. Concerns about how this pH relationship may affect exposure of juvenile loons to mercury pollution are discussed, as well as other potential causes of the survival—pH relationship. This will allow improved ecological risk assessments, which are important for the development of regulatory limits for chemical stressors. Thus, it is anticipated that this research will facilitate the criteria process.
Description:
Survival is a vexing parameter to measure in many young birds because of dispersal and delayed impacts of natal rearing conditions on fitness. Drawing upon marking and resighting records from an 18-year study of territorial behavior, we used Cormack-Jolly-Seber analysis with Program MARK to estimate juvenile survival and its predictors in a population of common loons (Gavia immer). In addition, we investigated predictors of chick mass, survival and inter sibling size disparity in two chick broods. Both small size and low pH of natal lakes predicted poor survival among chicks and juveniles; thus, features of the natal environment have both immediate and lasting effects on fitness. The pH × stage interaction retained in our MARK models indicates that the detrimental impact of lake chemistry on fitness diminishes with time; the retention of pH × lake size as a predictor of chick mass and condition pinpoints small lakes as those where acidity impacts chicks most severely. A simple adjustment for dispersal showed that juvenile survival to age three is at least 0.49, suggesting that loon populations are healthier than often supposed.