Geolocation reveals mid-continent migratory routes and Texas wintering areas of Red Knots Calidris canutus rufa

Red Knots Calidris canutus are commonly observed along the Texas coast during fall and spring. Although some significant winter records have been reported in Texas, it was previously unknown if birds were using Texas as a wintering area or primarily as a stopover area en route to more southerly wintering destinations. We fitted 69 Red Knots with geolocators on Mustang and Padre Islands between fall 2009 and fall 2010, and recovered eight of them between fall 2010 and spring 2012. The data showed that these knots: 1) spent nearly the entire nonbreeding phase of their annual cycle (78.4%) in the north-west Gulf of Mexico, 2) used the Mid-Continent (or Central) Flyway as a migratory route on both north and southbound migrations, 3) used stopover sites in the Northern Great Plains of the United States and Canada as well as the Nelson River Delta/Hudson Bay area, and 4) exhibited stronger consistency in timing of northbound migratory movements than in south-bound movements. For the two birds for which geolocator data included consecutive years of data, one showed consistency in northbound and southbound stopover location between years, while the other showed variability in northbound, but not southbound stopover locations. A geolocator recovered from a bird that was originally captured in the year in which it hatched showed that it also oversummered in Texas. The data further highlights the critical importance of the north-west Gulf of Mexico – particularly the Laguna Madre and Padre Island – for this population of Red Knots, and the need for further investigation to discover specific wintering sites.