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Using encounter rates as surrogates for density estimates makes monitoring of heavily-traded grey parrots achievable across Africa

  • Stuart J. Marsden (a1), Emmanuel Loqueh (a2), Jean Michel Takuo (a3), John A. Hart (a4), Robert Abani (a5), Dibié Bernard Ahon (a6), Nathaniel N. D. Annorbah (a1), Robin Johnson (a7) and Simon Valle (a1)...
Abstract
Abstract

Estimating population sizes in the heavily traded grey parrots of West and Central Africa would provide insights into conservation status and sustainability of harvests. Ideally, density estimates would be derived from a standardized 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 resources. We carried out line transect distance sampling alongside a simpler encounter rate method at 10 sites across five West and Central African countries. Density estimates were variable across sites, from 0–0.5 individuals km−2 in Côte d'Ivoire and central Democratic Republic of the Congo to c. 30 km−2 in Cameroon and > 70 km−2 on the island of Príncipe. Most significantly, we identified the relationship between densities estimated from distance sampling and simple encounter rates, which has important applications in monitoring grey parrots: (1) to convert records of parrot groups encountered in a day's activities by anti-poaching patrols within protected areas into indicative density estimates, (2) to confirm low density in areas where parrots are so rare that distance sampling is not feasible, and (3) 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−2 or lower, and local harvest should be disallowed on this basis.

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Corresponding author
(Corresponding author) E-mail s.valle@mmu.ac.uk
References
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AkaikeH. (1976) An information criterion. Mathematical Sciences, 14, 59.
AmunoJ.B., MassaR. & DranzoaC. (2007) Abundance, movements and habitat use by African grey parrots (Psittacus erithacus) in Budongo and Mabira forest reserves, Uganda. Ostrich, 78, 225231.
AmunoJ.B., MassaR. & OkethowengoG. (2010) Some observations on nesting African grey parrots, Psittacus erithacus, in Uganda. Rivista Italiana di Ornitologia, 80, 5759.
BensonC., BensonF., StuartS. & FryC. (1988) Parrots, parakeets and lovebirds. In The Birds of Africa (eds Fry C., Keith S. & Urban E.), pp. 125. Academic Press, London, UK.
BerkunskyI., CepedaR.E., MarinelliC., SimoyM.V., DanieleG., KacolirisF.P. et al. (2014) Occupancy and abundance of large macaws in the Beni savannahs, Bolivia. Oryx, http://dx.doi.org/10.1017/S0030605314000258
BibbyC.J., BurgessN.D., HillD.A. & MustoeS.H. (2000) Bird Census Techniques, 2nd edition. Academic Press, London, UK.
BirdLife International (2013a) Psittacus erithacus. In The IUCN Red List of Threatened Species v. 2014.3. Http://www.iucnredlist.org [accessed 26 May 2015].
BirdLife International (2013b) Psittacus timneh. In The IUCN Red List of Threatened Species v. 2014.3. Http://www.iucnredlist.org [accessed 26 May 2015].
BirdLife International (2014) Grey parrot Psittacus erithacus. Http://www.birdlife.org/datazone/speciesfactsheet.php?id=112657 [accessed 27 May 2015].
BucklandS.T., AndersonD.R., BurnhamK.P., LaakeJ.L., BorchersD.L. & ThomasL. (2001) Introduction to Distance Sampling: Estimating Abundance of Biological Populations. Oxford University Press, Oxford, UK.
BucklandS.T., LaakeJ.L. & BorchersD.L. (2010) Double-observer line transect methods: levels of independence. Biometrics, 66, 169177.
BucklandS.T., MarsdenS.J. & GreenR.E. (2008) Estimating bird abundance: making methods work. Bird Conservation International, 18, S91S108.
BurtonA.C., SamM.K., BalangtaaC. & BrasharesJ.S. (2012) Hierarchical multi-species modeling of carnivore responses to hunting, habitat and prey in a West African protected area. PLoS ONE, 7(5), e38007.
CarboneC., ChristieS., ConfortiK., CoulsonT., FranklinN., GinsbergJ.R. et al. (2001) The use of photographic rates to estimate densities of tigers and other cryptic mammals. Animal Conservation, 4, 7579.
CarboneC., ChristieS., ConfortiK., CoulsonT., FranklinN., GinsbergJ.R. et al. (2002) The use of photographic rates to estimate densities of cryptic mammals: response to Jennelle et al., Animal Conservation, 5, 121123.
CasagrandeD.G. & BeissingerS.R. (1997) Evaluation of four methods for estimating parrot population size. The Condor, 99, 445457.
CITES (2006) Twenty-second meeting of the Animals Committee, Lima, Peru. 7–13 July 2006. Http://www.cites.org/eng/com/ac/22/E22-10-2.pdf [accessed 27 May 2015].
CITES (2013) Strengthening Capacity for Monitoring and Regulation of International Trade of African Grey Parrot. Report prepared by BirdLife Africa Partnership Secretariat, Geneva, Switzerland.
CITES (2014) Convention on International Trade in Endangered Species of Wild Fauna and Flora. Appendices I, II and III. Http://cites.org/eng/app/appendices.php [accessed 31 October 2014].
CollarN.J. (2013) Timneh parrot and grey parrot represent two species. Http://stuartmarsden.blogspot.co.uk/2013/12/timneh-parrot-and-grey-parrot-represent.html [accessed 31 October 2014].
CollarN.J. & JuniperA.T. (1992) Dimensions and causes of the parrot conservation crisis. In New World Parrots in Crisis: Solutions from Conservation Biology (eds Beissinger S.R. & Snyder N.F.R.), pp. 124. Smithsonian Institution Press, Washington, DC, USA.
CougillS. & MarsdenS.J. (2004) Variability in roost size in an Amazona parrot: implications for roost monitoring. Journal of Field Ornithology, 75, 6773.
DändlikerG. (1992a) The Grey Parrot in Ghana: A Population Survey, a Contribution to the Biology of the Species, a Study of its Commercial Exploitation and Management Recommendations. A Report on CITES Project S-30. Unpublished report. CITES, Geneva, Switzerland.
DändlikerG. (1992b) Le Perroquet Gris (Psittacus erithacus) en Guinée. Evaluation des populations, contribution à la biologie, étude de l'exploitation commerciale et recommandations pour la gestion. Report sur le projet CITES S-30. Unpublished report. CITES, Geneva, Switzerland.
DanielsenF., BurgessN.D. & BalmfordA. (2005) Monitoring matters: examining the potential of locally-based approaches. Biodiversity and Conservation, 14, 25072542.
EspañolaC.P. (2013) Ecology and conservation of the parrots of Luzon, Philippines. PhD thesis. Manchester Metropolitan University, Manchester, UK.
EspinosaS., BranchL.C. & CuevaR. (2014) Road development and the geography of hunting by an Amazonian indigenous group: consequences for wildlife conservation. PLoS ONE, 9(12), e114916.
FigueiraL., TellaJ.L., CamargoU.M. & FerrazG. (2015) Autonomous sound monitoring shows higher use of Amazon old growth than secondary forest by parrots. Biological Conservation, 184, 2735.
HartT. (2009) A New Conservation Landscape for Bonobo: Discovery and Conservation of the Tshuapa-Lomami-Lualaba Landscape in the Democratic Republic of Congo. Lukuru Wildlife Research Foundation, Inc., U.S. Fish and Wildlife Service, Washington, DC, USA.
IUCN (2001) IUCN Red List Categories and Criteria. Version 3.1. IUCN Species Survival Commission, Gland, Switzerland and Cambridge, UK.
JamesA.N., GastonK.J. & BalmfordA. (1999) Balancing the Earth's accounts. Nature, 401, 323324.
JennelleC.S., RungeM.C. & MacKenzieD.I. (2002) The use of photographic rates to estimate densities of tigers and other cryptic mammals: a comment on misleading conclusions. Animal Conservation, 5, 119120.
JuniperT. & ParrM. (1998) Parrots: A Guide to Parrots of the World. Pica Press, Robertsbridge, UK.
LanciaR.A., NicholsJ.D. & PollockK.H. (1994) Estimating the number of animals in wildlife populations. In Research and Management Techniques for Wildlife and Habitats (ed. Bookhout T.A.), pp. 215253. The Wildlife Society, Bethesda, USA.
LeeA.T.K. & MarsdenS.J. (2012) The influence of habitat, season, and detectability on abundance estimates across an Amazonian parrot assemblage. Biotropica, 44, 537544.
LegendreP. & LegendreL. (1998) Numerical Ecology, 2nd edition. Elsevier, Amsterdam, The Netherlands.
LinkieM., ChapronG., MartyrD.J., HoldenJ. & Leader-WilliamsN. (2006) Assessing the viability of tiger subpopulations in a fragmented landscape. Journal of Applied Ecology, 43, 576586.
MacKenzieD.I., NicholsJ.D., LachmanG.B., DroegeS., RoyleJ.A. & LangtimmC.A. (2002) Estimating site occupancy rates when detection probabilities are less than one. Ecology, 83, 22482255.
MaiselsF., StrindbergS., BlakeS., WittemyerG., HartJ., WilliamsonE.A. et al. (2013) Devastating decline of forest elephants in central Africa. PLoS ONE, 8(3), e59469.
MarquesT.A., ThomasL., FancyS.G. & BucklandS.T. (2007) Improving estimates of bird density using multiple-covariate distance sampling. The Auk, 124, 12291243.
MarsdenS.J. (1999) Estimation of parrot and hornbill densities using a point count distance sampling method. Ibis, 141, 327390.
MarsdenS.J., CollarN.J. & WaughD. (2013) Zusammenbruch der Graupapageienbestände in Ghana. Papageien, 12, 425429.
MarsdenS.J. & RoyleK. (2015) Abundance and abundance change in the world's parrots. Ibis, 157, 219229.
MartinR.O., PerrinM.R., BoyesR.S., AbebeY.D., AnnorbahN.D., AsamoahA. et al. (2014) Research and conservation of the larger parrots of Africa and Madagascar: a review of knowledge gaps and opportunities. Ostrich, 85, 205233.
McGowanP. (2001) Status, Management and Conservation of the African Grey Parrot Psittacus erithacus in Nigeria. CITES, Geneva, Switzerland.
NadeauC.P. & ConwayC.J. (2012) Field evaluation of distance-estimation error during wetland-dependent bird surveys. Wildlife Research, 39, 311320.
NewsonS.E., EvansK.L., NobleD.G., GreenwoodJ.D.D. & GastonK.J. (2008) Use of distance sampling to improve estimates of national population sizes for common and widespread breeding birds in the UK. Journal of Applied Ecology, 45, 13301338.
NewtonI. (1994) The role of nest sites in limiting the numbers of hole-nesting birds: a review. Biological Conservation, 70, 265276.
OlmosF. & TurshakL. (2009) A survey of birds in Omo Forest Reserve, south-western Nigeria. African Bird Club Bulletin, 16, 184196.
PithonJ. & DythamC. (1999) Census of the British ring-necked parakeet Psittacula krameri population by simultaneous counts of roosts. Bird Study, 46, 112115.
PrimackR.B. (1993) Essentials of Conservation Biology. Sinauer Associates, Sunderland, USA.
R Development Core Team (2013) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing. Vienna, Austria.
RoveroF. & MarshallA.R. (2009) Camera trapping photographic rate as an index of density in forest ungulates. Journal of Applied Ecology, 46, 10111017.
RowleyI. & CollarN. (1997) Order psittaciformes. In Handbook of Birds of the World. Vol. 4, Sandgrouse to Cuckoos (eds del Hoyo J., Elliot A. & Sartagal J.), pp. 246477. Lynx Edicions, Barcelona, Spain.
RyanT.P. (1997) Modern Regression Methods. Wiley, New York, USA.
SamejimaH., OngR., LaganP. & KitayamaK. (2012) Camera-trapping rates of mammals and birds in a Bornean tropical rainforest under sustainable forest management. Forest Ecology and Management, 270, 248256.
SnyderN.F.R., McGowanP., GilardiJ.D. & GrajalA. (2000) Parrots: Status Survey and Conservation Action Plan 2000–2004. IUCN, Gland, Switzerland and Cambridge, UK.
SollmannR., MohamedA., SamejimaH. & WiltingA. (2013) Risky business or simple solution—relative abundance indices from camera-trapping. Biological Conservation, 159, 405412.
SutherlandW.J. (ed.) (2006) Ecological Census Techniques: A Handbook, 2nd edition. Cambridge University Press, Cambridge, UK.
ThomasL., BucklandS.T., RexstadE.A., LaakeJ.L., StrindbergS., HedleyS.L. et al. (2010) Distance software: design and analysis of distance sampling surveys for estimating population size. Journal of Applied Ecology, 47, 514.
UNEP–WCMC (2014) CITES trade database. Http://trade.cites.org/ [accessed 13 March 2015].
VittekM., BrinkA., DonnayF., SimonettiD. & DescléeB. (2014) Land cover change monitoring using Landsat MSS/TM satellite image data over West Africa between 1975 and 1990. Remote Sensing, 6, 658676.
ZylstraE.R., SteidlR.J. & SwannD.E. (2010) Evaluating survey methods for monitoring a rare vertebrate, the Sonoran desert tortoise. The Journal of Wildlife Management, 74, 13111318.
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