Implantable satellite transmitters (e.g., Model PTT-100, Microwave Telemetry, Inc) were incorporated into the study to provide fine-resolution location data for a sample of the adult male common loons fitted with geolocator tags in 2010 and 2011. Transmitters were implanted in the abdominal cavity following procedures developed by Korschgen et al. (1996). The satellite transmitters were programmed to transmit on a variable schedule based on the anticipated stage of migration during the loon’s annual cycle - 8 hours on:72 hours off during the breeding season, 8 hours on:24 hours off while migrating, 6 to 8 hours on:96 hours off on the wintering grounds, and 8 hours on:24 hours off during spring migration, and 8 hours on:96 hours off for the remaining life of the transmitter. Transmitter data, received by equipment on polar-orbiting National Oceanic and Atmospheric Administration Tiros-N weather satellites, were transmitted to the Service Argos data processing center in Landover, Maryland, where loon locations were estimated from the Doppler shift in the transmitter's carrier frequency. Location estimates were acquired using Argos Standard Service Processing (Argos Location Classes [LC] 3, 2, 1, and 0) and Auxiliary Location Processing (LC A, B, and Z). One standard deviation of nominal accuracy for location estimates with LC 3, 2, 1, and 0 are <250, 250 to 500, 500 to 1,500, and >1,500 m, respectively (Service Argos 2008). We utilized the most accurate locations per 8-hour transmission period for each individual to describe the daily location of that adult loon. Spot measurements of water depth and distance to shore were determined for each radiomarked loon location. Only location estimates for LC qualities 1-3 were used in the analyses.