The initial deadline for comments on this topic is 28 April 2014, and therefore later than for most other topics currently under discussion.
This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for non-passerines
Lynx Edicions and BirdLife International will soon publish the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.
The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.
Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.
The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 1 of the checklist (for non-passerines) will begin to be incorporated into the 2014 Red List update, with the remainder, and those for passerines (which will appear in volume 2 of the checklist), to be incorporated into subsequent Red List updates.
Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.
Clapper Rail Rallus longirostris is being split into R. longirostris, R. obsoletus and R. crepitans, following the application of criteria set out by Tobias et al. (2010).
Prior to the taxonomic change, R. longirostris (BirdLife species factsheet) was listed as being of Least Concern, on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria.
R. obsoletus (incorporating levipes, yumanensis and beldingi) is found along the western coasts of the USA and Mexico, disjunctly from San Francisco and San Pablo bays, California, south to Baja California Sur and southern Nayarit, Mexico.
The nominate form is confined to central California, mainly in San Francisco Bay and San Pablo Bay (and Suisun Bay; Overton 2007). Formerly, it also occurred in Morro, Tomales, Humboldt and Monterey Bays (Eddleman and Conway 1998). This form was originally threatened by hunting, but more contemporary threats include development for industry, agriculture, saltpans and urbanisation, leading to a drastic reduction in its habitat (Taylor and van Perlo 1998). By the late 1980s, c.85% of the species’s habitat in the 1850s had been lost, with much of the remaining habitat in a degraded state (Ehrlich et al. 1992). Urban development, pollution and introduced predators continue to pose major threats (Taylor and van Perlo 1998, Schwarzbach et al. 2006).
Since 2005, there has been a concerted and coordinated effort to monitor the population of obsoletus (Herzog et al. 2005, Liu et al. 2012a,b). Data suggest that the population was relatively stable in 2005-2007, but declined by 51% between 2007 and 2008, followed by an apparent weak recovery in 2009-2011 (Liu et al. 2012a,b). The population in 2009-2011 was estimated at 1,167 individuals (range 954-1,426) using both survey data and model predictions of densities for unsurveyed sites (Liu et al. 2012a,b). Application of the same methodology to data from 2005-2008 yields an average population estimate of 1,719 individuals (range 1,169 to 2,172) (Liu et al. 2012a).
The other west coast forms are also regarded as threatened. Form levipes has been estimated to number 190 pairs in the USA and c.240 pairs in Mexico (Eddleman et al. 1988, Ehrlich et al. 1992) and has lost huge areas of habitat, while form yumanensis has been estimated to number 1,700-2,000 individuals (Ehrlich et al. 1992) and has experienced increases and decreases in habitat availability, with habitat threatened overall with conversion and high water flows. A more recent population estimate, however, put the population at 6,629 individuals (95% CI: 4,859-8,399) in the Colorado River delta region of Mexico (Hinojosa-Herta et al. 2001). There are apparently no published population estimates for beldingi.
The total population of R. obsoletus may approach as few as 10,000 mature individuals, although there may be many more than 1,000 mature individuals in the largest sub-population, thus it is perhaps unlikely to qualify as Near Threatened under criterion C2. Note that the definition of sub-populations used in relation to the IUCN Red List criteria is of “geographically or otherwise distinct groups in the population between which there is little demographic or genetic exchange (typically one successful migrant individual or gamete per year or less)” (IUCN 2001). The overall population trend is thought to be negative, thus information is sought on whether the rate of decline could approach or exceed 30% over 14 years (estimate of three generations).
R. crepitans (incorporating waynei, saturatus, pallidus, grossi, belizensis, scotti, insularum, coryi, leucophaeus and caribaeus) is widespread and somewhat disjunctly distributed along the coasts of the eastern USA and Mexico, and the Caribbean, with isolated populations in Central America.
R. longirostris (as defined following the taxonomic change, and incorporating cypereti, phelpsi, margaritae, pelodramus and crassirostris) has a widespread but disjunct range along the northern and eastern coasts of South America, ranging south to extreme northern Peru and Santa Catarina state in Brazil.
It is suggested that R. crepitans and R. longirostris be listed as being of Least Concern, on the basis that they are not thought to approach the thresholds for Vulnerable under any of the IUCN Red List criteria, although it is acknowledged that they are both likely to be in on-going decline owing mainly to habitat loss.
Comments are invited and further information would be welcomed.
Eddleman, W. R. and Conway, C. J. (1998) Clapper Rail. In Poole, A. and Gill, F. (Eds.) The birds of North America. No. 340. Washington, D.C.: American Ornithologists’ Union.
Eddleman, W. R., Knopf, F. L., Meanly, B., Reid, F. A. and Zembal, R. (1988) Conservation of North American rallids. Wilson Bulletin 100: 458–475.
Ehrlich, P. R., Dobkin, D. S. and Wheye, D. (1992) Birds in jeopardy – the imperilled and extinct birds of the United States and Canada, including Hawaii and Puerto Rico. Stanford, CA: Stanford University Press.
Foin, T. C., Garcia, E. J., Gill, R. E., Culberson, S. D. and Collins, J. N. (1997) Recovery strategies for the California clapper rail (Rallus longirostris obsoletus) in the heavily-urbanized San Francisco estuarine ecosystem. Landscape and Urban Planning 38: 229–243.
Herzog, M., Liu, L., Evens, J., Nur, N. and Warnock, N. (2005) Temporal and Spatial Patterns in Population Trends in California Clapper Rail (Rallus longirostris obsoletus). 2005 Progress Report. Stinson Beach and Point Reyes, CA: PRBO Conservation Science and Avocet Research Associates.
Hinojosa-Huerta, O., DeStefano, S. and Shaw, W. W. (2001) Distribution and abundance of the Yuma clapper rail (Rallus longirostris yumanensis) in the Colorado River delta, Mexico. Journal of Araid Environments 49(1): 171–182.
IUCN (2001) IUCN Red List Categories and Criteria: Version 3.1. Gland, Switzerland and Cambridge, UK: IUCN Species Survival Commission.
Liu, L., Wood, J., Nur, N., Salas, L. and Jongsomjit, D. (2012a) California Clapper Rail (Rallus longirostris obsoletus) Population monitoring: 2005-2011. PRBO Technical Report to the California Department of Fish and Game. Petaluma, CA: PRBO Conservation Science.
Liu, L., Wood, J., Salas, L. and Nur, N. (2012b) 2011 Annual Report to U.S. Fish and Wildlife Service: California Clapper Rail (Rallus longirostris obsoletus) TE-807078-12. Submitted to U.S. Fish and Wildlife Service, Sacramento. Petaluma, CA: PRBO Conservation Science.
Overton, C. T. (2007) Data Summary: A Review of Literature Regarding California Clapper Rail (Rallus longirostris obsoletus) Demographics, Habitat Use, Home Range, Movements, and Effects of Disturbance. Prepared for State Coastal Conservancy, San Francisco Estuary Invasive Spartina Project. Dixon, CA: U.S. Geological Survey.
Schwarzbach, S. E., Albertson, J. D. and Thomas, C. M. (2006) Effects of predation, flooding, and contamination on reproductive success of California clapper rails (Rallus longirostris obsoletus) in San Francisco Bay. Auk 123(1): 45–60.
Taylor B. and van Perlo, B. (1998) Rails: A guide to the rails, crakes, gallinules and coots of the world. Robertsbridge, UK: Pica Press.
Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. (2010) Quantitative criteria for species delimitation. Ibis 152: 724–746.