The red knot, Calidris canutus, is a species of migratory shorebird that is currently listed as “near threatened” on the IUCN Red List; the subspecies Calidris canutus rufa is listed as a “threatened” species under the US Endangered Species Act. Causes of red knot population decline have not been clearly identified. Here I hypothesize that snow coverage declines in the high Arctic may be linked to red knot breeding success and to population declines in Florida. In this study, wavelet and crosswavelet analyses were used to identify temporal trends and relationships between changes in red knot populations and Arctic snow coverage. Strong El Niño Southern Oscillation events that occurred during the late 1970s through the 1980s appear to have contributed to a decline in snow cover, which was linked to the significant decline in the red knot population. The period of highest common power was predominated by antiphase trending, suggesting that red knot populations mirror snow coverage trends from 1982 to 1988, a period of maximum population decline.