SREL Reprint #1773
Applications of a modified Richards sigmoid model to assess the uptake and effects of environmental contaminants upon birds
I. Lehr Brisbin, Jr.
Abstract: The uptake of environmental contaminants by birds and other consumer organisms traditionally has been studied under controlled laboratory conditions and has been described with a fixed-shape monomolecular model. Under free-living field conditions, however, several species of birds utilizing both aquatic and terrestrial food webs have been shown to have a significant time lag in early contaminant uptake rates, with the resulting data being more accurately described by a flexibly shaped modified Richards sigmoid model. This same modified Richards model has also proved useful for describing changes in the growth of a variety of organisms, including birds, in response to exposures to a variety of stressors, such as uptake of environmental contaminants. The latter studies have shown that the shape of a bird's growth curve is more likely to change, and thus shape provides a more sensitive indicator of response to contaminant uptake than either the asymptotic size or rate at which overall growth occurs. Fixed-shape sigmoid models that fail to conform to the proper curve shape of the data being described can produce misleading or erroneous conclusions concerning the uptake or effects of contaminants upon birds. These errors can be particularly important in comparing contaminant uptake under field vs laboratory conditions and in assessing the effects of contaminant uptake upon growth.
Keywords: contaminants, birds, growth, sigmoid models, radionuclides
SREL Reprint #1773
Brisbin, I. L., Jr. 1994. Applications of a modified Richards sigmoid model to assess the uptake and effects of environmental contaminants upon birds. pp. 161-170 In: R. J. Kendall and T. E. Lacher, Jr. (Eds.). Proceedings of the Ninth Pellston Workshop: Wildlife Ecology and Population Modeling. Lewis Publishers, Boca Raton, FL.
This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).