Data Zone
Justification of Red List category
A moderately rapid to rapid reduction in the population of Short-billed Dowitcher is estimated to be taking place based on analysis of migration count and Breeding Bird Survey data. The magnitude of the trend is uncertain, and a proportion of the population is not sampled by these surveys, but the migration count survey is considered the most representative dataset for the species. Moderately rapid reductions are also evident from eBird data. Drivers of the recorded decline are uncertain, although likely a combination of threats identified for other declining shorebird species also apply here. The population size and range both remain large. On the basis of the rate of population reduction, Short-billed Dowitcher is assessed as Vulnerable.
Population justification
The global population is currently estimated at 245,000 mature individuals (Wetlands International 2023). Previously a lower value was estimated at 153,000 mature individuals (Andres et al. 2012), based on Jehl Jr. et al. (2020; first published in 2001). This estimates about 75,000 L. g. caurinus/Pacific populations and 78,000 L. g. hendersoni/griseus/Atlantic and Gulf coasts (Jehl Jr. et al. 2020). However more than 100,000 of the latter group were estimated to be breeding in Canada (Morrison et al. 1994), and this value is increased to 170,000 in Wetlands International (2023). A higher value of 320,000 was supplied for the United States Shorebird Conservation Plan (Brown 2001) and given the difficulty in adequately covering the population in either breeding or non-breeding areas this is a plausible high bound. The species is not covered by the Program for Regional and International Shorebird Monitoring (PRISM) surveys as it breeds further south, but the observation that these systematic surveys typically increased estimates significantly suggests the current population size may be conservative.
Trend justification
Analysis of migration count data estimates a moderate to extremely rapid reduction over the past three generations of -58% (-14 to -81% 90% credible intervals) (Smith et al. 2023). This data is also used for the trend in Partners in Flight (2023). Other data also indicate declines, but not at such severe rates. eBird data indicate a moderately rapid reduction between 14 and 23% over three generations (Fink et al. 2023), and Breeding Bird Survey (BBS) data estimate a 26% reduction over the 12 years between 2010 and 2022 (Ziolkowski et al. 2022), equal to the three-generation reduction after rounding. This latter rate has increased, with the equivalent rate derived from 2000-2022 data only 19%. Surveys of southbound migrants are thought to be the most representative data for deriving trends (ECCC 2019) and the network of sites covers the migration route of the eastern breeding range, but Alaskan breeding birds are not well covered. Pacific coast migration counts have not separated the two co-occurring dowitcher species: combined the species pair show a rapid reduction but this represents less than 5% of the global population (Migratory Shorebird Project, unpublished data). In contrast to the sources above, the Christmas Bird Count suggest an increasing trend within the USA and Canada (Meehan et al. 2022). Most of the population is outside of the USA during the non-breeding season, but this may reflect differing trends between subpopulations, indicating that the severe declines are occurring primarily in the populations migrating further, and along more easterly routes to winter in South America (G. Angelozzi-Blanco in litt. 2024). Alternatively it may represent shifts in the wintering distribution such that a greater number occur at more northern sites and are hence available to the CBC surveys (Smith et al. 2023). Overall, and accounting for the level of uncertainty in the migration count estimates, the rate of reduction is estimated at between 20-49% over the past three generations. This rate is projected to continue to one generation in the future, and while uncertainty is high it is suspected, given the absence of mitigation, to continue for the next three generations into the future.
Breeds from Kodiak Island and the Alaska Peninsula east through south coastal Alaska, United States of America (USA), northern British Columbia south to Queen Charlotte Island, Yukon and Northwest Territories inland to Alberta, Manitoba and south Hudson Bay, around James Bay and east to Quebec and central Labrador, Canada (Jehl Jr. et al. 2020). Recent data suggest that the species is now breeding in western Alaska (Fink et al. 2023), which may represent a westward shift in distribution. Three subspecies are recognised, L. g. griseus is the easternmost, breeding in Quebec and western Labrador, North Twin Island (Nunavut) in James Bay, while L. g. hendersoni breeds from Aksimiski Island in James Bay west to Alberta. L. g. caurinus occurs furthest west into Alaska. Winters along the coast, from southern USA (from north California on the Pacific and south Virginia on the Atlantic) south to central Peru, around the Gulf Coast and the Caribbean and from Colombia to east central Brazil (Jehl Jr. et al. 2020).
Confusion with L. scolopaceus has meant that many aspects of this species have remained poorly known until relatively recently (Jehl Jr. et al. 2020). It breeds in muskeg swamp in the subarctic taiga from the edge of the boreal forest just about to the tundra, uses scattered bushes or trees for display (Jehl Jr. et al. 2020). During the non-breeding season it occurs largely in coastal areas, preferring saltwater habitat and especially tidal mudflats rather than sandy substrates. Also occurs in flooded agricultural fields (Jehl Jr. et al. 2020).
Migration is typically undertaken along the coast, with Suriname seemingly the point of both northbound departure and southbound arrival for many individuals (Jehl Jr. et al. 2020). Feeds on invertebrates.
With little clear information on drivers of decline, and little evidence of obvious habitat loss, it is suspected but not clear that there is a reduction in at least the quality of the species' habitat. More research is required to understand if habitat area or extent is declining, and if it is the limiting factor for the species.
There is little clear evidence for the drivers of the recorded reductions. Effects of climate change have been predicted to cause increased risk to the species by affecting migration and non-breeding sites (Galbraith et al. 2014). Impacts of habitat change in coastal areas, either through development or disturbance may be affecting the species in northern South America and Central America, but evidence is lacking and there is only a reference that development of coastal lagoons in Venezuela may be an issue (Jehl Jr. et al. 2020). The species uses flooded agricultural fields in addition to natural coastal sites: it is not clear that habitat availability has greatly changed. The species breeds at the zone of transition along the northern edge of the boreal forest (Jehl Jr. et al. 2020): it is plausible though unstudied that climate impacts are affecting this zone that impact the species' reproductive success. It is possible that impacts of increasing populations of predators on breeding grounds may lead to increased adult mortality as well as reduced reproductive success.
Hunting may affect the easternmost portion of the population that migrates through the Caribbean. Dowitchers were not represented in subsistence hunting in Alaska (Naves et al. 2019). Hunting is still permitted on Saint Pierre and Miquelon (AFSI 2020), but numbers are unlikely to be significant. In the Caribbean Islands an index of harvest was judged to be moderately high (scoring three out of four) for the Caribbean Islands (AFSI 2020). The species accounted for 4-11% of the hunted total of shorebirds on Barbados, representing 700–2,400 individuals of the species taken based on mean harvest from 1988-2010 (Wege et al. 2014). The Potential Biological Removal (mean) derived for the species is 4,847 ± 1,252 individuals (Watts et al. 2015), suggesting that there is a plausible risk of unsustainable harvest in the species. The largest numbers of Short-billed Dowitcher in the Caribbean have been recorded from Cuba (Cañizares and Reed 2020), where there is no data on any harvest. Many also winter along the north coast of Brazil, where assessment of harvest is needed (AFSI 2020). However the harvest in Barbados has been reducing in recent years (Wege et al. 2014, AFSI 2020). None were recorded in markets for sale in Guyana, although the species is present, suggesting any harvest here is negligible (Andres et al. 2022).
Recreational disturbance is observed to be correlated with declines in counts at mudflat sites monitored over time (Drever et al. 2016), which may affect survival and condition ahead of the commencement of the breeding season.
Noted to have been a prime target of market hunters in the 19th century (Jehl Jr. et al. 2020), but there was no documentation of the extent of impacts on the species' status. It is believed to have suffered large population declines before recovering prior to the 1970s (Jehl Jr. et al. 2020).
Conservation Actions In Place
Investigations are underway to explore migratory connectivity using Motus tagged individuals (Graham 2022).
Conservation Actions Needed
The potential habitat changes plausibly impacting the species need to be investigated. Quantification of the current harvest is required. In Barbados, where there is a quantified level of harvest, consult with the Barbados Wildfowlers Association on further lowering bag limits for the species (Wege et al. 2014).
Text account compilers
Martin, R.
Contributors
Smith, P. A., Angelozzi-Blanco, G. & Davidson, P.
Recommended citation
BirdLife International (2024) Species factsheet: Short-billed Dowitcher Limnodromus griseus. Downloaded from
https://datazone.birdlife.org/species/factsheet/short-billed-dowitcher-limnodromus-griseus on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/12/2024.