Staging, an essential part of shorebird migration, is when birds concentrate in large numbers to rest and refuel. Abundance estimates at key staging sites offer promise to monitor many transient migrant populations; however, stopover chronology is needed. Point counts were conducted of all shorebirds staging at Chaplin and Reed Lakes, Saskatchewan, Canada (May-June 2014-2017). Stopover durations of individual Sanderlings (Calidris alba) were obtained using automated radio telemetry of individual Sanderlings tagged both locally and in the Gulf of Mexico (April-May 2015-2017). Seventeen Arctic-breeding shorebird species were recorded during point counts. Sanderlings were the most abundant and reached peak numbers during the last week of May. Estimates of Sanderling stopover duration varied by year and estimation method: “true stopover duration” (radio-tagged in Gulf of Mexico with known arrival and departure) was 11.1 days (95% CI = 8.6-13.6); “minimum stopover duration” (radio-tagged at Chaplin Lake with unknown arrival but known departure) was 11.9 days (95% CI = 11.1-12.7); and “estimated stopover duration” (Pradel Survival and Seniority models) was 19.9 days (95% CI = 17.5-22.7). Assuming an average 11-day stopover, we estimated ∼75,000 Sanderlings (Range = 56,000-91,000) or 12% of the global population use this site during spring migration. These findings highlight the importance of accurate migration chronology to monitor Arctic-breeding shorebird populations.