This discussion was first published on Nov 30 2010 as part of the 2010-2011 Red List update, but remains open for comment to enable reassessment in 2014.
Lesser Yellowlegs Tringa flavipes is listed as Least Concern on the basis that it is not believed to approach the thresholds for Vulnerable under any of the IUCN criteria. This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence less than 20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be negative, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (at least a 30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).
In recent years, evidence of declines in the population of T. flavipes has raised concerns over the species’s status. Data from the Breeding Bird Survey (BBS) suggest that it has undergone a large and statistically significant decrease in North America over the last 40 years (-94.9% decline over 40 years, equating to a -52.6% decline per decade; Butcher and Niven 2007); however, these surveys cover less than 50% of the species’s range in North America. Nevertheless, the decline suggested by the BBS data prompted the US Fish and Wildlife Service to add the species to the Birds of Conservation Concern 2008 report (B. Andres in litt. 2009, B. Andres per A. Lesterhuis in litt. 2009).
Following reported declines in the wintering population of T. flavipes in Suriname since the 1970s, surveys were carried out at one site in 2008-2009 using the methods of a previous survey at the same location (Ottema and Ramcharan 2009). The results showed that numbers of T. flavipes were down by c.80% on those recorded in 2002-2003. This change is assumed by Ottema and Ramcharan (2009) to be representative of the entire coast of Suriname, based on an aerial survey of the coast in December 2008, additional ground-based observations and four surveys at another location. Ottema and Ramcharan (2009) suggest that the global population may have declined by c.75% from 2002-2003 to 2008-2009, and that the species may face extinction within 20-30 years, citing Morrison and Ross’s (1989) observations from the mid-1980s that more than 70% of T. flavipes and Greater Yellowlegs T. melanoleuca wintering on the South American coast do so in Suriname. However, the non-breeding population may be shifting its geographical preferences, either along the coast of north-eastern South America or more widely; a possibility that cannot be eliminated owing to the limited scope of the fieldwork carried out in 2008-2009.
The uncertainties surrounding existing population data for T. flavipes seriously hinder attempts to estimate the global population trend. The species would be eligible for uplisting to Near Threatened under the A criterion if it was shown that it had undergone a decline approaching 30% over 17 years (estimate of three generations), and eligible for at least Vulnerable if the decline was estimated to be greater than 30%. Up-to-date information is requested on this species’s population trend and the severity of potential threats.
Butcher, G. S. and Niven, D. K. (2007) Combining Data from the Christmas Bird Count and the Breeding Bird Survey to Determine the Continental Status and Trends of North America Birds. Ivyland, PA: National Audubon Society.
Morrison, R. I. G. and Ross, R. K. (1989) Atlas of Nearctic shorebirds on the coast of South America. Two volumes. Canadian Wildlife Service Special Publication. Ottawa, Canada: Canadian Wildlife Service.
Ottema, O. H. and Ramcharan, S. (2009) Dramatic decline of Lesser Yellowlegs Tringa flavipes in Suriname. Wader Study Group Bull.: 116: 87-88.