By Mark P. Vrtiska
Ranchers and landowners who host migrating trumpeter swans each year often share a common question for biologists: “Is that the same pair of swans?” The answer, more than likely, is yes.
A recent study of 38 trumpeter swans captured and fitted with transmitters in the Sandhills found 80 percent of swans that nested at a particular wetland or lake came back to that same wetland or lake the following year. Their return to the same area each spring appears to be driven by their diet.
The largest waterfowl species on the planet, swans feed almost exclusively on submerged aquatic vegetation, which only grows in wetlands, creeks and rivers with good water quality and clarity. The swans likely return to these areas knowing there will be food to eat when they get there.
The swans’ fidelity — or rate of return — for wintering areas was similar, returning at a rate of just over 72 percent for all swans, and 79 percent for swans with cygnets. It should be noted, however, that all of the swans that were tracked returned to the wintering area from the previous year at one time or another.
Once swans migrated to a wintering area, they spent almost 77 percent of their time there, but did move some, using two to three areas during the winter. Again, there was some unanticipated variation in their use of small creeks where swan use had not been previously documented. Known for being very territorial, there was never more than one nesting pair on a wetland or lake in the Sandhills during this study.
The future of trumpeter swans in Nebraska and elsewhere depends on the conservation and management of breeding and wintering areas with abundant, submergent aquatic vegetation. Eliminating or reducing carp, soil runoff, invasive plants and other factors will ensure they have access to those resources they need.
Swans are the big, white “canaries” of high-quality wetlands, lakes, creeks and rivers, and their status are an indication in how good a job we’re doing in conserving those areas, but also our own environment.
Mark P. Vrtiska is a professor of practice of wildlife management at UN-L’s School of Natural Resources.