Winter movements and site fidelity of Trumpeter Swans (Cygnus buccinator) in the Nebraska Sandhills
By Mark P. Vrtiska, Dessalegn Ejigu, and Larkin A. Powell
Trumpeter Swans (Cygnus buccinator) were reintroduced into the Nebraska Sandhills, a region comprising one of the largest remaining contiguous grasslands in the world, in the 1960s but knowledge of the ecology of these birds is limited. Although relatively unaltered, anthropogenic changes may impact this population of swans.
Trumpeter swans (Cygnus buccinator) in the Nebraska Sandhills. Photo by Colleen Childers.
Trumpeter Swans inhabiting the Nebraska Sandhills are part of the High Plains Flock of the Interior Population and mainly breeds and winters within the Sandhills. Although the population’s size is increasing, the genetic diversity of the population is low and new conservation threats, such as the development of wind farms and associated power lines, depletion or removal of groundwater, and other habitat alterations are looming. Managers need more information related to swans’ wintering ecology. The objective of our study was to describe and quantify winter movements and fidelity of Trumpeter Swans in the Nebraska Sandhills. This information would assist in current conservation planning as well as meeting future challenges in implementing appropriate management efforts.
Trumpeter swan (Cygnus buccinator) fitted with neck collar.
We captured swans during remige molt and fitted selected swans with a neck collar (red with white lettering) with a unique alphanumeric code with an attached solar-powered, global positioning system (GPS), platform transmitting terminal (PTT) transmitter (collar and transmitter mass. Transmitters were programmed to obtain 5 locations/day during 1 November–31 March which encapsulated the wintering period for swans in the Sandhills.
We examined fidelity and movements at 2 different scales within Nebraska: (1) large-scale wintering “complexes” that represented the major rivers and creeks and (2) smaller-scale wintering “sites” that represented tributaries to those major rivers and creeks that comprised each complex. The 2 scales allowed for a more conservative approach in representing swan movements that differentiated between moving to a tributary (i.e., short movement) vs. a different river or creek system (i.e., larger movement). We also designated sites within complexes from examining and using concentrations of locations of marked birds.
Only one swan made a long-distance movement out of Nebraska during the winter. Mean distance (6SD) moved from breeding or post-breeding areas to their initial wintering complex was 53.4 (652.7) km. As we suspected, swans spent most (77.2%) of their time on one wintering complex and 75% of their time at one wintering site. Swan fidelity (proportion returning) to wintering complexes was 0.72 and to wintering sites was 0.69. Return rate to their primary wintering complex and site was 100%. Fidelity rates to wintering complexes of swans with cygnets at time of capture and those without were 0.79 and 0.55, respectively. Swan movements in the Nebraska Sandhills indicate that they are willing to move among areas but show fidelity to wintering areas. Changes in wintering habitat may alter patterns of fidelity, but swans may be able to adapt and move to alternative areas. Rivers, creeks, and other areas are important to wintering swans breeding in the Sandhills and contribute to the sustainable conservation of swans.
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