The Red Knot ( Calidris canutus rufa ) decline in the western hemisphere: is there a lemming connection?

• Published in: Canadian Journal of Zoology
• Main Authors: Fraser, J.D., Karpanty, S.M., Cohen, J.B., Truitt, B.R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2013
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Arctic; Canada; Calidris canutus; Fennoscandia; Red Knot
• Online Access: http://dx.doi.org/10.1139/cjz-2012-0233; http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjz-2012-0233; http://www.nrcresearchpress.com/doi/pdf/10.1139/cjz-2012-0233

Numbers of Western Atlantic Red Knots (Calidris canutus rufa (A. Wilson, 1813)) have declined since 1980, with a sustained downward trend observed after 1998. Because the reproductive output of a closely related Eurasian subspecies (Calidris canutus islandica (L., 1767)) is known to be low when lemming numbers are low, and because lemming cycles in Fennoscandia were recently interrupted, we investigated the relationship between the rodent cycle in arctic Canada and numbers of C. c. rufa migrating through the United States. Shooting records from Cape Cod in the 1800s and Red Knot counts on the Delaware Bay from 1986 to 1998 cycled with 4-year periods. Annual peaks in numbers of Red Knots stopping in the Delaware Bay in 1986–1998 occurred 2 years after arctic rodent peaks more often than expected at random. The results suggest that the reproductive output of C. c. rufa was linked to the rodent cycle before the Red Knot decline. There is no evidence that such a link existed after 1998. These findings are consistent with the hypothesis that an interruption of the rodent cycle in Red Knot habitat could have been a driver in the recent Red Knot decline. Field studies in the Arctic are needed to further investigate this hypothesis.