Evaluation of Translocation Criteria for Trumpeter Swans Reintroduced to Northern Utah: Habitat Quality and Interactions with Tundra Swans

• Main Author: Engelhardt, Katharina A. M.
• Format: Text
• Language: unknown
• Published: DigitalCommons@USU 1997
• Subjects: Evaluation; Translocation Criteria; Trumpeter Swans; Northern Utah; Habitat Quality; Interactions; Tundra Swans; Animal Sciences; Aquaculture and Fisheries; Cygnus columbianus; Tundra
• Online Access: https://digitalcommons.usu.edu/etd/4421; https://doi.org/10.26076/2048-b134; https://digitalcommons.usu.edu/context/etd/article/5454/viewcontent/1997_Engelhardt_Katharina.pdf

Fifty-seven Trumpeter swans (Cygnus buccinator) were translocated to the Bear River Migratory Bird Refuge and the Bear River Club Company in northern Utah. The purpose of this effort was to encourage dispersal of the Rocky Mountain population of Trumpeter swans during the winter, and to reestablish a migratory route to southern wintering grounds. I assessed the success of the translocation by evaluating 13 translocation criteria proposed in the literature. In this study I addressed two of these criteria in detail by evaluating habitat quality at the translocation sites and by analyzing potential competitive interactions with Tundra swans (Cygnus columbianus). Habitat quality was determined by analyzing the spatial distribution of sago pondweed (Potamogeton pectinatus) tubers in wetland sediments before the fall and after the spring migration of Tundra swans. Sixty-four transects were established within the study sites with 10 sediment cores per transect. Geostatistical procedures were employed to account for autocorrelation between samples. Tuber biomass was not randomly distributed within the studied wetlands. In fact, discrete areas of high values appeared to exist before and after swan foraging . It is not likely that sago pondweed tubers are limiting swan abundance in this system. Thus, the habitat quality of the study sites is sufficient for Trumpeter swan translocation. Potential competitive interactions with Tundra swans were evaluated by examining differences in resource utilization patterns of the two species. I measured body size differences, dietary overlap, resource availability, and the efficiency of extracting available resources. Trumpeter swans appear to benefit from a larger body size and a longer neck because they are more efficient in extracting tubers from the sediment, and are able to exploit tubers to a greater sediment depth than Tundra swans. However, Trumpeter swans incur higher traveling costs due to the larger body size. The trade-off between higher foraging efficiency of Trumpeter ...