Endemic to Mauritius, the Pink Pigeon (Nesoenas mayeri) numbered only 12 wild individuals in 1986 (see Mauritian Wildlife Foundation webpage; http://www.mauritian-wildlife.org/application/index.php?tpid=30&tcid=33). Intensive conservation efforts have aided the recovery of the species, combatting threats such as habitat loss, predation by and competition with introduced mammals and birds, as well as disease outbreaks (e.g. Jones and Owadally 1988, Reese Lind 1991, Swinnerton 2001, Swinnerton et al. 2005, Bunbury et al. 2008). These conservation efforts have included: a captive breeding programme with releases and translocations conducted between wild populations; supplementary feeding; control of introduced predators; disease management; habitat protection and habitat restoration (see Jones et al. 2013).
Thanks to these conservation efforts the population has increased to >300 known individuals in the wild and the population has been roughly stable since the early 2000s (C. Jones, V. Tatayah and N. Zuel in litt. 2017). The species does show population fluctuations, and it appears to be on one of the downward trends of these fluctuations currently. However, since exceeding 300 known individuals in the wild the population has never dipped below this figure with lows of c.325 individuals. There are plans for the setting up of further subpopulations and the population living in the wild is hoped to increase in line with these (C. Jones and V. Tatayah in litt. 2017). Therefore, given this information we have reassessed the species here, and assessed it under all Red List Criteria.
Criterion A – Over the past 3 generations (c.17 years) the population has been roughly stable, although with some fluctuations. Therefore, it does not warrant listing as threatened under this criterion.
Criterion B – The species has an Extent of Occurrence (EOO) of 320km2, which meets the threshold value for Endangered under criterion B1. The Area of Occupancy (AOO) has not been directly calculated, but given the species’ EOO falls below the threshold AOO value (500km2) it likely meets the threshold for Endangered under criterion B2 too. However, to be listed as such would require at least two other conditions to also be met.
With the setting up of an eighth sub-population (C. Jones in litt. 2017) the species may now occur at 8 locations*, yet because one of these has only been set up in the last year then it should not be counted in a Red List assessment yet (per IUCN Guidelines; IUCN Standards and Petitions Subcommittee 2017). Therefore, it should likely be listed as occurring at 7 locations, and the species is not severely fragmented. Therefore, this would at best meet the threshold for Vulnerable under subcriterion a.
The species is not thought to be undergoing a continuing decline in EOO, AOO, number of locations or population size. The ongoing long-term conservation work also would suggest that there is no longer a continuing decline in area/quality of habitat where the species is currently found. Therefore, it would not meet the conditions for subcriterion b.
Finally, while the species does show population fluctuations, these are not of the scale required to be considered as ‘extreme fluctuations’ by IUCN guidelines (fluctuation in the scale of an order of magnitude; IUCN Standards and Petitions 2017). Therefore, it would not meet the conditions for subcriterion c.
Thus the species would not warrant listing as threatened under criterion B. However, as the species may have qualified as threatened under criterion B were it not for continued conservation efforts, it may warrant listing as Near Threatened under criteria B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v).
Criterion C – The population is considered to be stable, yet fluctuating. Therefore, even though the population size is very small, it would not warrant listing as threatened under this criterion. However, as this is likely to be the result of conservation efforts, it may warrant listing as Near Threatened under criterion C2a(i).
Criterion D – Despite being roughly stable, the population does show fluctuations. Since the population reached the level around which it appears to be stable (c.380 individuals C. Jones, V. Tatayah and N. Zuel in litt. 2017) the known wild population has ranged from c.325 to c.410 individuals, while the possible wild population has ranged from c.375 to c.490 individuals (N. Zuel in litt. 2017). IUCN Guidelines stipulate that when a population shows fluctuations it is best practice to take into account the lower limit rather than focussing just on the average (IUCN Standards and Petitions Subcommittee 2017). However, it is tentatively assessed that the population size numbers >250 mature individuals, and so would fall in the range 250-999 mature individuals that qualifies the species as Vulnerable under criterion D1.
Criterion E – To the best of our knowledge there has been no quantitative analysis of extinction risk conducted for this species. Therefore, it cannot be assessed against this criterion.
Therefore, it is tentatively proposed that the species be listed as Vulnerable under criterion D1. Comments are welcome, but please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’ Red List status. Therefore, please make sure your comments are relevant to the species’ Red List status.
*The term ‘location’ refers to a distinct area in which a single threatening event can rapidly affect all individuals of the taxon present, with the size of the location depending on the area covered by the threatening event. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat (IUCN 2001, 2012).
Bunbury, N.; Jones, C. G.; Greenwood, A. G.; Bell, D. J. 2008. Epidemiology and conservation implications of Trichomonas gallinae infection in the endangered Mauritian Pink Pigeon. Biological Conservation 141(1): 153-161.
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.
IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K. Available at: www.iucnredlist.org/technical-documents/categories-and-criteria.
IUCN Standards and Petitions Subcommittee. 2017. Guidelines for Using the IUCN Red List Categories and Criteria. Version 13. Prepared by the Standards and Petitions Subcommittee. Downloadable from http://www.iucnredlist.org/documents/RedListGuidelines.pdf.
Jones, C. G.; Bunbury, N.; Zuel, N.; Tatayah, V.; Swinnerton, K. J. 2013. Pink Pigeon Nesoenas mayeri. In: Safford, R. J.; Hawkins, A. F. A. (ed.), The Birds of Africa. Vol. VIII: The Malagasy Region, pp. 484-489. Christopher Helm, London.
Jones, C. G.; Owadally, A.W. 1988. The life histories and conservation of the Mauritius Kestrel Falco punctatus, Pink Pigeon Columba mayeri and Echo Parakeet Psittacula eques. Proceedings of the Royal Society of Arts and Sciences of Mauritius 5: 79-130.
Reese Lind, C. 1994. Management of the EEP Pink Pigeon Columba (Nesoenas) mayeri population. Dodo: Journal of the Jersey Wildlife Preservation Trust 30: 106-113.
Swinnerton, K. 2001. Ecology and conservation of the Pink Pigeon Columba mayeri on Mauritius. Dodo: Journal of the Jersey Wildlife Preservation Trust 37: 99.
Swinnerton, K.J.; Greenwood, A. G.; Chapman, R.E.; Jones, C. G. 2005. The incidence of the parasitic disease trichomoniasis and its treatment in reintroduced and wild Pink Pigeons Columba mayeri. Ibis 147: 772-782.