The recent use of abdominally-implanted satellite transmitters to track movements of waterfowl is rapidly filling gaps in our understanding of their population structure and affinities. However, premature loss of transmitter signals is of serious concern. Such loss occurred in 21 out of 25 satellite transmitters implanted in Harlequin Ducks (Histrionicus histrionicus) in 1996-1998. The tracking of eight birds captured while migrating along the shores of Forillon National Park, Gaspé Peninsula, Québec, and the resightings of some of these birds after transmitter failure is detailed. The birds were followed for three to 373 d (mean = 127 d, SD = 82 d) until transmitter signal was lost, but four birds were resighted 493 to 1,474 d after the surgical procedures. These results indicate that premature failure of the transmitter is a common cause of signal loss, even when the battery voltage is adequate at the time of loss. Harlequin Ducks drakes implanted with satellite radios are able to live long after the transmitter has failed.