Hostname: page-component-76fb5796d-2lccl Total loading time: 0 Render date: 2024-04-25T14:38:57.950Z Has data issue: false hasContentIssue false

Population status of the endemic Pitcairn Reed Warbler Acrocephalus vaughani on Pitcairn Island, South Pacific

Published online by Cambridge University Press:  30 January 2024

Steffen Oppel*
Affiliation:
RSPB Centre for Conservation Science, Royal Society for the Protection of Birds, David Attenborough Building, Cambridge, UK Swiss Ornithological Institute, 6204 Sempach, Switzerland
Robert Eisler
Affiliation:
RSPB Centre for Conservation Science, Royal Society for the Protection of Birds, David Attenborough Building, Cambridge, UK
Nik Aspey
Affiliation:
RSPB Centre for Conservation Science, Royal Society for the Protection of Birds, David Attenborough Building, Cambridge, UK
*
Corresponding author: Steffen Oppel; Email: steffen.oppel@vogelwarte.ch

Summary

Reed warblers are widespread throughout Eurasia, Africa, and Australasia, and many species undertake long seasonal migrations. By contrast, other species of the genus Acrocephalus are sedentary and endemic to single oceanic islands. The Pitcairn Reed Warbler Acrocephalus vaughani is confined to the small volcanic island of Pitcairn in the South Pacific Ocean, and no population assessments have ever been conducted for this species. Due to its restricted range, the presence of invasive species, and the loss of natural habitat, the species is considered as globally “Endangered”, but its actual conservation status is entirely speculative. We conducted transect surveys and nest monitoring in the austral summer of 2022/23 and present abundance estimates for the species. We counted between 51 and 158 reed warblers along 54 transects that were each 100 m long and covered all habitats and roughly 13% of the vegetated island area. Using binomial mixture models accounting for imperfect detection and habitat variation in abundance, we estimated that Pitcairn may hold 1,568 (95% confidence interval 812–3,237) Pitcairn Reed Warblers, and that the species appeared to be most abundant in introduced Rose Apple Syzygium jambos stands. Based on the monitoring of 49 nests, of which only four failed to fledge any young, we estimated that Mayfield nest survival rate was 0.69 and estimated productivity was 1.07 (± 0.39 standard deviation) fledglings per nest. Assuming that Pitcairn Reed Warblers have similar annual survival probabilities as other island reed warblers, the productivity appears sufficient to maintain the population and there is no indication that the species has decreased significantly over the past three generations. Given the limited extent of occurrence, and the stable current population size between 442 and 2,774 mature individuals, we recommend that the global conservation status of the Pitcairn Reed Warbler be classified as “Vulnerable”.

Type
Research Article
Copyright
© Royal Society for the Protection of Birds, 2024. Published by Cambridge University Press on behalf of BirdLife International

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bell, B.D. (2018). From wetlands to islands: morphological variation, plumage and song in Pacific island Acrocephalus warblers. Notornis 65, 202222.Google Scholar
BirdLife International (2023). Species Factsheet: Acrocephalus vaughani. BirdLife International. http://datazone.birdlife.org/species/factsheet/pitcairn-reed-warbler-acrocephalus-vaughani.Google Scholar
Bond, A.L., Brooke, M.D.L., Cuthbert, R.J., Lavers, J.L., McClelland, G.T.W., Churchyard, T. et al. (2019). Population status of four endemic land bird species after an unsuccessful rodent eradication on Henderson Island. Bird Conservation International 29, 124135.CrossRefGoogle Scholar
Brooke, M.d.L. (1995). The breeding biology of the gadfly petrels Pterodroma spp. of the Pitcairn Islands: characteristics, population sizes and controls. Biological Journal of the Linnean Society 56, 213231.CrossRefGoogle Scholar
Brooke, M.d.L. (2019). Rat eradication in the Pitcairn Islands, South Pacific: a 25-year perspective. In Veitch, C.R., Clout, M.N., Martin, A.R., Russell, J.C. and West, C. J. (eds), Island Invasives: Scaling Up To Meet the Challenge. Gland: International Union for Conservation of Nature, pp. 9599.Google Scholar
Brooke, M.d.L. and Hartley, I.R. (1995) Nesting Henderson Reed-warblers (Acrocephalus vaughani taiti) studied by DNA fingerprinting: unrelated coalitions in a stable habitat? The Auk 112, 7786.Google Scholar
Brooke, M.d.L., Jones, P., Vickery, J. and Waldren, S. (1996). Seasonal patterns of leaf growth and loss, flowering and fruiting on a subtropical central Pacific island. Biotropica 28, 164179.CrossRefGoogle Scholar
Camp, R.J., Pratt, T.K., Marshall, A.P., Amidon, F. and Williams, L.L. (2009). Recent status and trends of the land bird avifauna on Saipan, Mariana Islands, with emphasis on the endangered Nightingale Reed-warbler Acrocephalus luscinia. Bird Conservation International 19, 323337.CrossRefGoogle Scholar
Cibois, A., Beadell, J.S., Graves, G.R., Pasquet, E., Slikas, B., Sonsthagen, S.A. et al. (2011). Charting the course of reed‐warblers across the Pacific islands. Journal of Biogeography 38, 19631975.CrossRefGoogle Scholar
Cibois, A., Thibault, J.-C. and Pasquet, E. (2008). Systematics of the extinct reed warblers Acrocephalus of the Society Islands of eastern Polynesia. Ibis 150, 365376.CrossRefGoogle Scholar
Claverie, M., Ju, J., Masek, J.G., Dungan, J.L., Vermote, E.F., Roger, J.-C. et al. (2018). The harmonized Landsat and Sentinel-2 surface reflectance data set. Remote Sensing of Environment 219, 145161.CrossRefGoogle Scholar
Dinerstein, E., Olson, D., Joshi, A., Vynne, C., Burgess, N.D., Wikramanayake, E. et al. (2017). An ecoregion-based approach to protecting half the terrestrial realm. BioScience 67, 534545.CrossRefGoogle ScholarPubMed
Fantle-Lepczyk, J.E., Berry, L., Lepczyk, C., Duffy, D.C. and Conant, S. (2018). Key demographic factors for recovery of the endangered Nightingale Reed-Warbler (Acrocephalus hiwae) via population viability analysis. Avian Conservation and Ecology 13, 13.CrossRefGoogle Scholar
Fiske, I. and Chandler, R. (2011). unmarked: An R package for fitting hierarchical models of wildlife occurrence and abundance. Journal of Statistical Software 43, 123.CrossRefGoogle Scholar
Graves, G.R. (1992). The endemic land birds of Henderson Island, southeastern Polynesia: notes on natural history and conservation. The Wilson Bulletin 104, 3243.Google Scholar
Hering, J. and Fuchs, E. (2009). The Cape Verde Warbler. British Birds 102, 1724.Google Scholar
Howell, S.N.G. and van der Vliet, R.E. (2014). Endemic landbirds of Pitcairn and Henderson, South Pacific. Dutch Birding 36, 332339.Google Scholar
IUCN (2017). IUCN Red List of Threatened Species. Version 2017-1. Gland: International Union for Conservation of Nature. https://www,iucnredlist.org.Google Scholar
Johnson, T.F., Brown, T.J., Richardson, D.S. and Dugdale, H.L. (2018). The importance of post-translocation monitoring of habitat use and population growth: insights from a Seychelles Warbler (Acrocephalus sechellensis) translocation. Journal of Ornithology 159, 439446.CrossRefGoogle Scholar
Jones, C.W., Risi, M.M., Osborne, A.M., Parker, G.C., Rexer-Huber, K., Le Bouard, F. et al. (2020). Abundance, distribution and breeding success of the endemic Gough Island Finch Rowettia goughensis between 2009 and 2018. Emu – Austral Ornithology 120, 230238.CrossRefGoogle Scholar
Keast, A. (1970). Adaptive evolution and shifts in niche occupation in island birds. Biotropica 2, 6175.CrossRefGoogle Scholar
Kéry, M. (2008). Estimating abundance from bird counts: binomial mixture models uncover complex covariate relationships. The Auk 125, 336345.CrossRefGoogle Scholar
Kéry, M. and Royle, J.A. (2016). Applied Hierarchical Modeling in Ecology: Analysis of Distribution, Abundance and Species Richness in R and BUGS: Volume 1: Prelude and Static Models. Amsterdam: Elsevier Science.Google Scholar
Kéry, M., Royle, J.A. and Schmid, H. (2005). Modeling avian abundance from replicated counts using binomial mixture models. Ecological Applications 15, 14501461.CrossRefGoogle Scholar
Kéry, M. and Schaub, M. (2012). Bayesian Population Analysis Using WinBUGS. Oxford: Academic Press.Google Scholar
Kingston, N. and Waldren, S. (2003). The plant communities and environmental gradients of Pitcairn Island: The significance of invasive species and the need for conservation management. Annals of Botany 92, 3140.CrossRefGoogle ScholarPubMed
Komdeur, J. (1992). Importance of habitat saturation and territory quality for evolution of cooperative breeding in the Seychelles warbler. Nature 358, 493495.CrossRefGoogle Scholar
Leisler, B. and Schulze-Hagen, K. (2011). The Reed Warblers: Diversity in a Uniform Bird Family. Radolfzell: Max-Planck Institute for Ornithology/KNNV Publishing.CrossRefGoogle Scholar
Mayfield, H.F. (1975). Suggestions for calculating nest success. The Wilson Bulletin 87, 456466.Google Scholar
Murray, N.J., Keith, D.A., Simpson, D., Wilshire, J.H. and Lucas, R.M. (2018). REMAP: An online remote sensing application for land cover classification and monitoring. Methods in Ecology and Evolution 9, 20192027.CrossRefGoogle Scholar
Oppel, S., Cassini, A., Fenton, C., Daley, J. and Gray, G. (2014). Population status and trend of the Critically Endangered Montserrat Oriole. Bird Conservation International 24, 252261.CrossRefGoogle Scholar
Parashuram, D., Oppel, S., Fenton, C., James, G., Daley, J., Gray, G. et al. (2015). The Forest Thrush Turdus lherminieri prefers mature mesic forest with dense canopy. Bird Conservation International 25, 503513.CrossRefGoogle Scholar
Reichel, J.D., Wiles, G.J. and Glass, P.O. (1992). Island extinctions: the case of the endangered Nightingale Reed-Warbler. The Wilson Bulletin 104, 4454.Google Scholar
Royle, J.A. and Nichols, J.D. (2003). Estimating abundance from repeated presence-absence data or point counts. Ecology 84, 777790.CrossRefGoogle Scholar
Royle, J.A., Nichols, J.D. and Kéry, M. (2005). Modelling occurrence and abundance of species when detection is imperfect. Oikos 110, 353359.CrossRefGoogle Scholar
Schmidt, J.H., McIntyre, C.L. and MacCluskie, M.C. (2013). Accounting for incomplete detection: What are we estimating and how might it affect long-term passerine monitoring programs? Biological Conservation 160, 130139.CrossRefGoogle Scholar
Sillett, T.S., Chandler, R.B., Royle, J.A., Kéry, M. and Morrison, S.A. (2012). Hierarchical distance-sampling models to estimate population size and habitat-specific abundance of an island endemic. Ecological Applications 22, 19972006.CrossRefGoogle ScholarPubMed
Steadman, D.W. (2006). Extinction and Biogeography of Tropical Pacific Birds. Chicago: University of Chicago Press.Google Scholar
Tarwater, C.E. (2010). The Pre-reproductive Period in a Tropical Bird: Parental Care, Dispersal, Survival, and Avian Life Histories. PhD dissertation, University of Illinois, Urbana.Google Scholar
Thibault, J. and Cibois, A. (2006). The natural history and conservation of Acrocephalus rimitarae, the endemic reed-warbler of Rimatara Island, Oceania. Bulletin of the British Ornithologists’ Club 126, 201207.Google Scholar
Thibault, J.-C., Martin, J.-L., Penloup, A. and Meyer, J.-Y. (2002). Understanding the decline and extinction of monarchs (Aves) in Polynesian Islands. Biological Conservation 108, 161174.CrossRefGoogle Scholar
VanderWerf, E.A., Pierce, R., Bebe, R. and Taabu, K. (2016). Habitat use and status of the Bokikokiko or Christmas Island Warbler (Acrocephalus aequinoctialis). Pacific Science 70, 410, 437446.CrossRefGoogle Scholar
Waldren, S., Florence, J. and Chepstow-Lusty, A.J. (1995). A comparison of the vegetation communities from the islands of the Pitcairn Group. Biological Journal of the Linnean Society 56, 121144.CrossRefGoogle Scholar
Waldren, S., Weisler, M.I., Hather, J.G. and Morrow, D. (1999). The non-native vascular plants of Henderson Island, South-Central Pacific Ocean. Atoll Research Bulletin 463, 459465.CrossRefGoogle Scholar
Wiles, G.J., Bart, J., Beck, R.E. Jr and Aguon, C.F. (2003). Impacts of the Brown Tree Snake: Patterns of decline and species persistence in Guam’s avifauna. Conservation Biology 17, 13501360.CrossRefGoogle Scholar
Williams, G.R. (1960). The birds of the Pitcairn Islands, central south Pacific Ocean. Ibis 102, 5870.CrossRefGoogle Scholar
Supplementary material: File

Oppel et al. supplementary material

Oppel et al. supplementary material
Download Oppel et al. supplementary material(File)
File 16.1 KB