The Southeastern U.S. as a complex of use sites for nonbreeding rufa Red Knots: Fifteen years of band-encounter data

Abstract

Shorebirds have been banded for decades and monitoring programs have helped to accumulate large band-encounter datasets from across the globe; however, many of these datasets are left largely unused, particularly those collected by citizen scientists. These datasets can provide valuable insight into the migration and movement strategies of shorebirds and the threats they face throughout their migratory cycle. We used long-term (2003–2018) band-encounter data of Red Knots Calidris canutus rufa in North America to determine: (1) the spatiotemporal distribution during the nonbreeding season, (2) site fidelity to nonbreeding sites, and (3) migratory connectivity of knots using the southeastern United States (Southeast), an important overwintering and stopover area for this subspecies. Annual mean site fidelity ranged from 0% to 86% across 24 sites. We found movement between sites across the Southeast during migratory and wintering periods, indicating that knots are using the region as interconnected sites, as opposed to relying on a single site or a cluster of adjacent sites. We identified ‘hop migration’ as a common strategy for knots in the region, and showed regular within-year movement between sites in South Carolina, Georgia, and Florida. The Southeast is an understudied part of the rufa range; our results show the importance of the region to the subspecies both as a stopover and wintering area. Despite the inherent biases in the data and imperfect detection due to inconsistent survey effort, the data showed large-scale movements and confirmed the region as a complex of sites connected by knots.