Using encounter rates as surrogates for density estimates makes monitoring of heavily-traded grey parrots achievable across Africa S TUART J. M ARSDEN ,E MMANUEL L OQUEH ,J EAN M ICHEL T AKUO ,J OHN A. H ART R OBERT A BANI ,D IBIÉ B ERNARD A HON ,N ATHANIEL N. D. A NNORBAH R OBIN J OHNSON and S IMON V ALLE Abstract Estimating population sizes in the heavily traded grey parrots of West and Central Africa would provide in- sights into conservation status and sustainability of harvests. Ideally, density estimates would be derived from a standar- dized method such as distance sampling, but survey efforts are hampered by the extensive ranges, patchy distribution, variable abundance, cryptic habits and high mobility of the parrots as well as by logistical difficulties and limited re- sources. We carried out line transect distance sampling alongside a simpler encounter rate method at  sites across five West and Central African countries. Density estimates were variable across sites, from –. individuals km - in Côte d’Ivoire and central Democratic Republic of the Congo to c.  km - in Cameroon and .  km - on the island of Príncipe. Most significantly, we identified the rela- tionship between densities estimated from distance sam- pling and simple encounter rates, which has important applications in monitoring grey parrots: () to convert re- cords of parrot groups encountered in a day’s activities by anti-poaching patrols within protected areas into indicative density estimates, () to confirm low density in areas where parrots are so rare that distance sampling is not feasible, and () to provide a link between anecdotal records and local density estimates. Encounter rates of less than one parrot group per day of walking are a reality in most forests within the species’ ranges. Densities in these areas are expected to be one individual km - or lower, and local harvest should be disallowed on this basis. Keywords Africa, distance sampling, encounter rate, grey parrot, monitoring, population estimates, Psittacidae To view supplementary material for this article, please visit http://dx.doi.org/./S Introduction P opulation estimates and trends in abundance are essen- tial for the development of coherent conservation and management plans for wild animal species (Primack, ; Newson et al., ) and form the cornerstones of the IUCN Red List scheme (IUCN, ). For species that are har- vested from the wild and traded internationally, population monitoring is a legal requirement imposed by CITES (). With high numbers of threatened species and limited re- sources available (James et al., ), there is a need for prac- tical, rapid and inexpensive methods to provide usable metrics of animal abundance (Lancia et al., ; Carbone et al., ). As a result of habitat alteration and direct exploitation for the pet trade, parrots are one of the most threatened groups of birds (Collar & Juniper, ; Snyder et al., ). The grey parrots Psittacus spp., now classified as two species (Collar, ), grey parrot Psittacus erithacus (Central Africa to eastern Côte d’Ivoire; Fig. ) and timneh parrot Psittacus timneh (western Côte d’Ivoire to Guinea-Bissau), have a history of exploitation for national and international trade. During – . , wild-caught individuals entered international trade (UNEP–WCMC, ), with Cameroon being the main exporter and with , individuals exported legally during – (BirdLife International, ). The true size of the harvest (both past and present) may be much higher as mortality within the trade is likely to be high and illegal trade is impossible to monitor. There is concern that harvest levels are unsustain- able (CITES, ). Both species are categorized as Vulnerable on the IUCN Red List because of numerous an- ecdotal reports of declines and local extinctions, making population estimation and monitoring a conservation STUART J. MARSDEN,NATHANIEL N. D. ANNORBAH and SIMON VALLE (Corresponding author) School of Science & the Environment, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, UK. E-mail s.valle@mmu.ac.uk EMMANUEL LOQUEH Society for the Conservation of Nature in Liberia, Monrovia, Liberia JEAN MICHEL TAKUO Cameroon Biodiversity Conservation Society, Yaoundé, Cameroon JOHN A. HART Lukuru Foundation, Circleville, Ohio, USA, and Kinshasa, Democratic Republic of the Congo ROBERT ABANI SOS Nature, Kisangani, Democratic Republic of the Congo DIBIÉ BERNARD AHON SOS-FORETS, Campus Universitaire d’Abidjan-Cocody, Centre National de Floristique, Côte d’Ivoire ROBIN JOHNSON BirdLife International–Africa Partnership Secretariat, Nairobi, Kenya Received  November . Revision requested  January . Accepted  March . First published online  September . Oryx, 2016, 50(4), 617–625 © 2015 Fauna & Flora International doi:10.1017/S0030605315000484 https://doi.org/10.1017/S0030605315000484 Downloaded from https://www.cambridge.org/core. IP address: 54.70.40.11, on 25 Jul 2019 at 02:58:04, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms.