Aerial surveys in January 2018 of the rufa Red Knot (Calidris canutus) population wintering in Tierra del Fuego, South America, revealed a total of 9,840 birds. This is a 25% decrease on the number recorded in January 2017 (13,127), and marginally the lowest recorded since the surveys began (the previous low was 9,850 birds in 2011). While the population has not been showing any signs of a sustained recovery (there were 50,000 birds as recently as 2000), a 15% increase in the total counted between 2016 and 2017 had been a promising sign. Unfortunately it seems likely that poor northbound feeding conditions in Delaware Bay (USA) in May 2017 resulted in lowered survival, with the population crashing to a new low.
In 2018, nearly all the Red Knot counted were found in Bahía Lomas, Chile. Bahía Lomas became a WHSRN site of Hemispheric Importance in 2009, primarily for its unparalleled importance for rufa Red Knot. 98.7% of the birds counted in the 2018 survey occurred in Tierra del Fuego, which has been the case since 2011. At the other major historical wintering area in Río Grande, Argentina, the count improved slightly from the all-time low of 27 in 2017, with 130 birds recorded in the vicinity of the Interpretation Centre. Counts at Río Grande were in the range 3,500 to 5,000 as recently as 2008, but have fallen drastically since then. No Red Knot were recorded in Bahía San Sebastian amongst the much larger numbers of Hudsonian Godwits (Limosa haemastica). The concentration of nearly all the Red Knot in one location (Bahía Lomas), and in one major flock, makes them particularly vulnerable to any environmental problems that might occur locally.
A flock of rufa Red Knots as seen during the aerial survey. Photo: Antonio Larrea.
Delaware Bay plays a key role in the annual cycle of rufa Red Knot, as it is the last stopover on northward spring migration before the flight to the Arctic. It is here that the birds must acquire sufficient body reserves not only for the flight to the Arctic, but also to enable them to breed successfully once they arrive. Knots departing Delaware Bay in sub-optimal condition suffer lower survival, as shown by research in the early 2000s, when food resources (Horseshoe Crab eggs) were severely depleted, and many birds could not reach adequate departure weights – resulting in reduced survival and the rapid population crash observed in those years. In May 2017, low water temperatures in Delaware Bay resulted in a delay in Horseshoe Crabs coming ashore to lay their eggs, which in turn resulted in lowered availability of their eggs to migrating shorebirds. As a result, many knots departed Delaware Bay at lower than optimal weight levels, in fact at levels similar to those of the early 2000s when the population crashed.
Bahía Lomas and Bahía San Sebastian (Argentina) are also both major wintering areas for Hudsonian Godwit. Numbers of godwits in both Bahía San Sebastian (19,800) and Bahía Lomas (15,750) were higher than in 2017, the combined total of 35,550 compared with 24,900 the previous year. However, totals of godwits have varied between about 24,000 and 40,000 from 2011 to 2018, and worryingly these totals are lower than those in the early 2000s, suggesting a steady decrease since 2002.
The survey crew for the Bahía Lomas flight. Left to right: Capt. Francisco Esquivel, Dr. Guy Morrison, Sra. Jocelyn Velasquez, Sr. Antonio Larrea. Photo: Guy Morrison.
The 2018 surveys were conducted by Guy Morrison, Antonio Larrea, Jocelyn Velasquez, Adriana Mamani,and Ignacio Monteagudo, with the support of the pilots Francisco Esquivel (Chile) and Santiago de Larminat (Argentina). The surveys were made possible thanks to the Bobolink Foundation in support of the Atlantic Flyway Shorebird Initiative, as well as generous support from Larry Niles through USFWS-NMBCA and NFWF projects. Funding was also provided by an anonymous Canadian donor, and Guy Morrison used funds from the Allan Baker Award for Lifetime Achievement in Shorebird Conservation to support the work. We acknowledge and thank ENAP (Chile’s National Petroleum Company) for its ongoing logistic support and providing the helicopter for the surveys.
For more information, please contact Guy Morrison (rigmorrison@gmail.com).
