This discussion was first published as part of the 2013 Red List update, but remains open for comment to enable reassessment in 2014.
Crossley’s Ground-thrush Zoothera crossleyi is found in south-eastern Nigeria (on the Obudu and Mambilla Plateaux and Gotel Mountains), Cameroon (from Mt Cameroon and the Rumpi Hills in the south-west to Mt Tchabal Mbabo on the Adamawa Plateau [Dowsett-Lemaire and Dowsett 1999]), southern Congo and north-east Democratic Republic of Congo (DRC) (Urban et al. 1997). It is listed as Near Threatened under criterion B1ab(i,ii,iii) because it was thought to have a moderately small range threatened by agricultural encroachment and logging, and was suspected to be in decline owing to on-going habitat destruction and fragmentation (del Hoyo et al. 2005).
However, recent mapping of the species’s range suggests that its Extent of Occurrence (EOO) is larger than previously thought at an estimated 79,000 km2. Thus, it does not appear to approach the IUCN thresholds for Vulnerable under the range size criteria and could warrant downlisting to Least Concern if it is not found to approach any other thresholds for classification as Vulnerable. The population size has not yet been quantified but the species is described as rare to locally fairly common (del Hoyo et al. 2005). Given its relatively large range size, it seems unlikely that this species would have a population size approaching 10,000 mature individuals and so would not qualify as threatened or Near Threatened on population size under the C criterion. If, however, the species has experienced declines over the past three generations or 10 years (whichever is longer), approaching 30%, it may warrant listing as Near Threatened based on population declines under the A criterion of the IUCN Red List.
Comments on the population trends of this species and its proposed downlisting to Least Concern are welcomed.
del Hoyo, J., Elliott, A. and Christie, D. (2005) Handbook of the Birds of the World, vol. 10: Cuckoo-shrikes to Thrushes. Barcelona, Spain: Lynx Edicions.
Dowsett-Lemaire, F. and Dowsett, R. J. (1999) Survey of birds and amphibians on Mt Manenguba, Mt Nlonako, north Bakossi and around Kupe in 1988-99.
Urban, E. K., Fry, C. H. and Keith, S. (1997) The birds of Africa vol. V. London, UK: Academic Press.