RIPARIAN BIRDS AND BATS RELY ON FOOD CHAINS THAT BEGIN IN RIVERS.
Breeanne K. Jackson; Yosemite National Park; PO Box 700, El Portal, CA, 95318; (209) 379-1454; breezy_jackson@nps.gov; Sarah L. Stock, Leila S. Harris, Joseph M. Szewczak, Lynn N. Schofield, Michelle A. Desrosiers
River regulation can modify natural flow regimes with deleterious effects on aquatic communities. While the effects of flow manipulation on the physical environment and populations and assemblages of aquatic organisms has been described more thoroughly, how and to what extent river regulation influences ecosystem processes like food-web architecture is less studied. Emergent aquatic insect prey can provide an important food resource to riparian birds and bats with concomitant consequences for nutrient cycling through aquatic-terrestrial food webs. We used stable isotopes of carbon and nitrogen to compare food web architecture (trophic position and reliance on an aquatic-nutritional pathway) leading to birds and bats between a regulated river system and an unregulated river system located on the west slope of the Sierra Nevada, CA. We found that both birds and bats derived greater than 50% of their nutrition from food webs supported by photosynthesis by algae. In addition, bats occupied a similar trophic position to predatory fish in other systems. We observed no difference in food web architecture leading to birds and bats attributable to river regulation despite strong reliance on aquatic-terrestrial food webs.
Ecology and Conservation of Birds II