In migratory species. the timing of arrival at the breeding grounds is a life-history trait with major fitness consequences. The optimal arrival date varies from year-to-year. and animals use cues to adjust their arrival dates to match this annual variation. https://www.roneverhart.com/Seagate-Exos-7E2-ST1000NM0008-1TB-7-2K-RPM-SATA-6Gb-s-512n-128MB-3-5-Hard-Drive/