Molt migration is an annual movement from the breeding grounds to a different, distant molting area often north of the breeding grounds. Such movements are only completed by a segment of a population, typically nonbreeding individuals or failed breeders. Although molt migration is common among waterfowl, especially large-bodied species such as geese, it remains unknown whether the Trumpeter Swan (Cygnus buccinator), a species whose population is rapidly growing and expanding throughout the mid-continental United States, engages in molt migration. Here, we provide the first empirical description of an apparent molt migration of a nonbreeding male Trumpeter Swan using location data collected by a GPS-GSM collar. The swan departed its natal wetland in north-central Iowa, USA, on 1 June 2019 and arrived at a complex of small wetlands near Great Slave Lake in the Northwest Territories, Canada, on 4 July 2019, a straight-line distance of 2,420 km. For the next 43 d, the swan restricted its movements to a small wetland with a mean distance between sequential points of 126.15 m (range = 0.33–2,910.72 m), suggesting it was flightless during this time period. Both the timing and duration of this presumed flightless period coincide with the second prebasic molt in swans.

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