Justification of Red List Category
This species has not been recorded with certainty since 1963 (and none have been confirmed on the wintering grounds since 1939). It was formerly abundant, but declined rapidly over a century ago as a result of hunting and habitat loss and is now considered likely to be extinct (Elphick et al. 2010, Roberts and Jari? 2016). However, some uncertainty of the species's extinction status remains (Roberts and Jari? 2016, D. Roberts in litt. 2016). A set of papers published in 2017 (Akcakaya et al. 2017, Keith et al. 2017, Thompson et al. 2017) laid out methods for quantitatively estimating a species’s probability of extinction based on parameters associated with threats, in addition to records and surveys. Based on the application of these methods (Butchart et al. 2018), this species would qualify for reclassification as Critically Endangered. However, the authors recommended retaining it as Critically Endangered (Possibly Extinct) because the many claimed records since the last confirmed one (1963) all have a very low probability of being valid.
Any remaining population is assumed to be tiny (numbering fewer than 50 individuals and mature individuals), as there have been no confirmed sightings since the early 1960s.
The population trend of this species is unknown since the last confirmed sightings of this species occurred in the early 1960s.
Numenius borealis bred at (and presumably between) the Bathurst peninsula and Point Lake in Northwest Territories, Canada (Gill et al. 1998), and perhaps also Alaska, USA (Craig 2019). Birds migrated across Hudson Bay to Labrador (and New England, USA), and through the Caribbean to Argentina (especially the Pampas), and possibly Uruguay, Paraguay (R. Clay in litt. 2003), southernmost Brazil and Chile south to Patagonia (Gill et al. 1998). The return migration was probably along the Pacific coast, through Central America, across the Gulf of Mexico to the Texas coast and northwards through the prairies. It probably numbered hundreds of thousands, but declined rapidly in the 1870s-1890s to become very rare in the 20th century (Gill et al. 1998, Graves 2010). The last irrefutable record was of a specimen collected in Barbados in 1963 (Roberts et al. 2010). Since then there have been no confirmed records (none from the wintering grounds in South America since 1939), only several unconfirmed reports during 1981-2006 (Gill et al. 1998, M. Parr in litt. 2003, C. L. Gratto-Trevor in litt. 2004, R. Hoffman in litt. 2006, N. Crockford in litt. 2008), with the latest unconfirmed sighting from Barbados in September 2012 (E. Reed in litt. 2012). The population (if one persists) must be tiny (Gill et al. 1998). Analyses based on historic sightings found that the species's population likely collapsed in in the first decade of the 20th century and most likely went extinct in the late 1960s, with an upper limit to the confidence interval of 1977 (Elphick et al. 2010, Craig 2019). However, a new analysis that incorporated sighting uncertainty (Roberts and Jari? 2016) concluded that the species is possibly extinct but that there is a level of uncertainty that would suggest that the species's extinction is not yet confirmed (D. Roberts in litt. 2016). A set of papers published in 2017 (Akcakaya et al. 2017, Keith et al. 2017, Thompson et al. 2017) laid out methods for quantitatively estimating a species’s probability of extinction based on parameters associated with threats, in addition to records and surveys. Based on the application of these methods (Butchart et al. 2018), this species would qualify for reclassification as Critically Endangered. However, the authors recommended retaining it as Critically Endangered (Possibly Extinct).
It bred (May-August) in treeless arctic tundra at 180-335 m, comprising grassy meadows with birch (Betula) and sedge (Carex) (Gill et al. 1998). On autumn migration (July-October), it favoured ericaceous heath, crowberries Empetrum nigrum, pastures and intertidal flats (Gill et al. 1998). Winter habitat was possibly wet pampas grasslands, intertidal and semi-desert areas (Gill et al. 1998). On return migration (March-May), it favoured burnt areas in tall grass and mixed-grass prairies, and Rocky Mountain Grasshopper Melanoplus spretus was a key food source (Gill et al. 1998). It was gregarious, with traditional autumn migration sites (Gill et al. 1998).
Large-scale spring hunting in North America partially explains the species's potential extinction, but there was no recovery after hunting was outlawed and abandoned in c.1916 (Gill et al. 1998). The main cause is almost certainly the near total loss of prairies to agriculture, compounded by the suppression of prairie wildfires and the extinction of M. spretus (Gill et al. 1998). The widespread conversion of the pampas began after the main decline, but has hindered any possible recovery (Gill et al. 1998).
Conservation Actions Underway
CITES Appendix I. CMS Appendix I and II. It is protected in the USA, Canada, Argentina and Mexico. Its status has been fully documented, and identification details publicised (Gill et al. 1998). Breeding and wintering areas have been surveyed, and reported breeding sites investigated (Blanco et al. 1993, Gill et al. 1998, C. L. Gratto-Trevor in litt. 1999). An Environment Canada species recovery plan recommends that no recovery action be undertaken other than continued monitoring of reported sightings (Environment Canada 2007).
Conservation Actions Proposed
Continue cooperative international assessments of historical sites (Blanco et al. 1993, C. L. Gratto-Trevor in litt. 1999). Survey heath tundra along the Labrador coast during August-September and historic breeding grounds prior to the initiation of development projects (C. L. Gratto-Trevor in litt. 1999). Investigate any credible sightings (C. L. Gratto-Trevor in litt. 1999). Expand prairie habitat, and employ prescribed burnings (C. L. Gratto-Trevor in litt. 1999).
29-34 cm. Small cinnamon-coloured curlew. Similar spp. Little Curlew N. minutus is similar, but N. borealis is larger, longer winged (extending beyond tip of tail), shorter legged, cinnamon not buffish below with heavily barred breast and "Y" shaped marks on flanks. Small size (25% smaller than Whimbrel N. phaeopus) eliminates all other species. Voice Flight call reportedly a rippling tr-tr-tr and a soft whistle bee bee.
Text account compilers
Everest, J., Hermes, C., Smith, D., Wheatley, H.
Ashpole, J, Benstead, P., Bird, J., Butchart, S., Clay, R.P., Crockford, N., Elphick, C., Gill, R.E., Gratto-Trevor, C.L., Hoffman, R., Isherwood, I., Parr, M.J., Pilgrim, J., Reed, E., Roberts, D., Sharpe, C.J., Swem, T., Symes, A. & Wege, D.
BirdLife International (2023) Species factsheet: Numenius borealis. Downloaded from http://datazone.birdlife.org/species/factsheet/eskimo-curlew-numenius-borealis on 01/06/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://datazone.birdlife.org on 01/06/2023.