Letitia Grenier
Environmental Science, Policy and Management Dept.
University of California
151 Hilgard Hall, #3110
Berkeley, CA 94720-3110
lgrenier@nature.berkeley.edu
New Insights into the Salt Marsh Food Chain
 During 2002 I analyzed data on the salt marsh food web and Song Sparrow habitat values. For the stable isotope study of the food web, I analyzed another 100 samples and found some surprising results. Contrary to my prediction, the influence of tide and runoff does not appear to transfer a significant amount of food materials between the different salt marsh microhabitats. This finding is significant, because it means that animals living in tidal channels are not eating foods derived from the marsh plain and vice versa. Therefore, contaminants in one microhabitat are not likely to be transferred via biotic pathways to wildlife in other microhabitats. I will be presenting these results at the State of the Estuary Conference in January 2003 in Sacramento, CA, and I think they will be of interest to scientists and managers working on contaminants and marsh restoration on the Pacific Coast.
Second, I analyzed data on sparrow behavior to understand how they use the different areas of the marsh. Again, contrary to the expected result, I found that the birds defended areas along the tidal channels but foraged mainly on the marsh plain. These findings contribute greatly to our understanding of the habitat requirements of these threatened birds, because the literature discusses their dependence on tidal channels, rarely mentioning the marsh plain. I found that sparrows are eating a novel food type -- semi-terrestrial amphipods -- on the marsh plain. These results may guide design of restored marshes by ensuring that extensive marsh plain areas are included, rather than a focus on tidal channels alone. This is also a highly unusual territory type for Song Sparrows and adds to the basic science of avian behavioral ecology.
The grant from the Garden Club financed my 2003 field season, which was very successful. I monitored 40 territories and 65 nests this past spring. The funds were also used for purchasing supplies for preparation of the stable isotope samples for the food web study. My sincerest thanks to the members of the Garden Club of America for their support and generosity. This grant has enabled me to add another year of data to my study and significantly improve my dissertation research.
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