Abstract
Population monitoring of seabirds plays an important role in conservation since it provides the information required to evaluate conservation programmes of endangered species, to guide harvest management and to monitor indicators of marine ecosystem health. Annual nest counts are often used for the long-term monitoring of breeding seabird populations. While such counts provide a direct and cost-effective survey method, single nest counts will almost always yield an underestimate of the true number of nests and provide no means of expressing uncertainty. In this study, we used double counts and the Lincoln–Petersen estimator to assess the reliability of nest counts for the Yellow-Eyed Penguin (Megadyptes antipodes) in the South Island of New Zealand. We estimated the detection rate of single nest counts at 88%, and we calculated that double counts are sufficiently precise to detect changes in the size of the breeding population as small as 3.3% between years. We failed to detect observer bias or any effects of search effort or habitat on the detection rate, the only significant factor being the steepness of the terrain. Given the high detection rate and the susceptibility of Yellow-Eyed Penguins to human disturbance, we conclude that the established protocol for single nest counts is adequate for the regular monitoring of the population. We suggest that double counts could be conducted once every 5 years to obtain precise estimates for the purpose of long-term population monitoring. We also highlight the importance of repeating similar studies for a variety of species and habitats.
Zusammenfassung
Der Gelbaugenpinguin (Megadyptes antipodes) als Fallstudie zur Bewertung der Zuverlässigkeit von Nestzählungen
Bestandszählungen von Seevögeln spielen eine wichtige Rolle im Naturschutz. Sie stellen grundlegende Information bereit für die Bewertung von Naturschutzmaßnamen zum Erhalt gefährdeter Arten, als Orientierungshilfe für Ertragsmanagement, und zur Überwachung von Bioindikatoren mariner Ökosysteme. Jährliche Nestzählungen sind eine verbreitete Methode für Langzeitbeobachtungen von Brutpopulationen. Obwohl dies eine direkte und kosteneffektive Erfassungsmethode ist, bedeuten einmalige Nestzählungen fast immer eine Unterschätzung des tatsächlichen Brutbestands, ohne dabei eine Fehlerabschätzung zu erlauben. In dieser Studie testen wir Doppelzählungen und den Lincoln-Petersen-Index zur Bewertung der Zuverlässigkeit von Nestzählungen beim Gelbaugenpinguin (Megadyptes antipodes) auf der Südinsel von Neuseeland. Wir konnten zeigen, dass bei einmaligen Nestzählungen etwa 88% der Nester gefunden werden. Doppelzählungen waren genügend präzise, um Brutbestandsschwankungen von nur 3,3% zwischen den Jahren festzustellen. Wir konnten keine Unterschiede zwischen Beobachtern (z. B. Sucherfahrung) oder mögliche Auswirkungen von Suchintensität oder Bruthabitat auf den Sucherfolg finden. Allein die Steilheit des Geländes wirkte sich signifikant negativ auf den Sucherfolg aus. Da die Zuverlässigkeit von einmaligen Nestzählungen hinreichend genaue Ergebnisse lieferte und Gelbaugenpinguine sehr empfindlich sind gegenüber antropogenen Störungen, halten wir die etablierten einfachen Nestzählungen für die jährliche Brutbestandserfassung für angemessen. Wir empfehlen Doppelzählungen alle fünf Jahre durchzuführen, um präzise Daten für Langzeitpopulationsentwicklungen zu erhalten. Wir denken es ist wichtig, vergleichbare Studien an anderen Arten und in verschiedenen Habitaten zu wiederholen.
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References
Bart J, Droege S, Geissler P, Peterjohn B, Ralph CJ (2004) Density estimation in wildlife surveys. Wildl Soc Bull 32:1242–1247
Becker PH, Nagel R (1983) Schatzung des Brutbestandes der Silbermowe (Larus argentatus) auf Mellum, Langeoog und Memmert mit der Linientransekt-Methode. Die Vogelwelt 104:35–39
Croxall JP, Rothery P (1990) Population regulation of seabirds: implications of their demography for conservation. In: Perrins CM, LeBreton JD, Hirons GM (eds) Bird population studies: their relevance to conservation and management. Oxford University Press, Oxford, pp 272–296
Darby JT, Dawson SM (2000) Bycatch of Yellow-eyed Penguins (Megadyptes antipodes) in gillnets in New Zealand waters 1979–1997. Biol Conserv 93:327–332
Darby JT, Seddon PJ (1990) Breeding biology of Yellow-eyed Penguins (Megadyptes antipodes). In: Davis LS, Darby JT (eds) Penguin biology. Academic Press, Orlando, pp 45–62
Diamond AW, Devlin CM (2003) Seabirds as indicators of changes in marine ecosystems: ecological monitoring on Machias Seal Island. Environ Monit Assess 88:153–175
Dodd MG, Murphy TM (1995) Accuracy and precision of techniques for counting great blue heron nests. J Wildl Manag 59:667–673
Ellenberg U, Setiawan AN, Cree A, Houston DM, Seddon PJ (2007) Elevated hormonal stress response and reduced reproductive output in Yellow-eyed Penguins exposed to unregulated tourism. Gen Comp Endocrinol 152:54–63
Ellenberg U, Mattern T, Seddon PJ (2009) Habituation potential of Yellow-eyed Penguins depends on sex, character and previous experience with humans. Anim Behav 77:289–296
Erwin RM (1981) Censusing wading bird colonies: an update on the “flight-line” count method. Colon Waterbirds 4:91–95
Frederick PC, Heath JA, Bennets R, Hafner H (2006) Estimating nests not present at the time of breeding surveys: an important consideration in assessing nesting populations. J Field Ornithol 77:212–219
Furness RW, Camphuysen K (1997) Seabirds as monitors of the marine environment. J Mar Sci 54:726–737
Goldsmith EB (ed) (1991) Monitoring for conservation and ecology. Chapman and Hall, London
Harris MP (1989) Variation in the correction factor used for converting counts of individual Guillemots Uria aalge into breeding pairs. Ibis 131:85–93
Hutchinson AE (1979) Estimating numbers of colonial nesting seabirds: a comparison of techniques. Proc Colon Waterbird Group 3:235–244
IUCN (International Union for Conservation of Nature) (2010) IUCN red list of threatened species. Version 2010.2. Available at: http://www.iucnredlist.org. Accessed 9 Aug 2010
Lalas C, Jones PR, Jones J (1999) ) The design and use of a nest box for Yellow-eyed Penguins Megadyptes antipodes—a response to a conservation need. Mar Ornithol 27:199–204
Lancia RA, Nichols JD, Pollock KH (1996) Estimating the number of animals in wildlife populations. In: Bookhout TA (ed) Research and management techniques for wildlife and habitats. The Wildlife Society, Bethesda, pp 215–253
Link WA, Sauer JR (1997) New approaches to the analysis of population trends in land birds: comment. Ecology 78:2632–2634
Massaro M, Blair D (2003) Comparison of population numbers of Yellow-eyed Penguins, Megadyptes antipodes, on Stewart Island and on adjacent cat-free islands. NZ J Ecol 27:107–113
Mattern T, Ellenberg U, Houston D, Davis LS (2007) Consistent foraging routes and benthic foraging behaviour in Yellow-eyed Penguins. Mar Ecol Prog Ser 343:295–306
McClung MR, Seddon PJ, Massaro M, Setiawan AN (2004) Nature-based tourism impacts on Yellow-eyed Penguins Megadyptes antipodes: does unregulated visitor access affect fledging weight and juvenile survival? Biol Conserv 119:279–285
McKay R, Lalas C, McKay D, McConkey S (1999) Nest-site selection by Yellow-eyed Penguins Megadyptes antipodes on grazed farmland. Mar Ornithol 27:29–35
McKinley B (2001) Hoiho (Megadyptes antipodes) recovery plan. Department of Conservation, Wellington
Miskelly CM, Dowding JE, Elliott GP, Hitchmough RA, Powlesland RG, Robertson HA, Sagar PM, Scofield RP, Taylor GA (2008) Consevration status of New Zealand birds, 2008. Notornis 55:117–135
Moore PJ (1992) Breeding biology of the Yellow-eyed Penguin Megadyptes antipodes on Campbell Island. Emu 92:157–162
Moore PJ (1994) What is a bad season for Yellow-eyed Penguins? Department of Conservation, Wellington
Moore PJ (1999) Foraging range of the Yellow-eyed Penguin Megadyptes antipodes. Mar Ornithol 27:49–58
Moore PJ (2001) Historical records of Yellow-eyed Penguin (Megadyptes antipodes) in southern New Zealand. Notornis 48:145–156
Moore PJ, Fletcher D, Amey J (2001) Population estimates of Yellow-eyed Penguins, Megadyptes antipodes, on Campbell Island, 1987–98. Emu 101:225–236
Nettleship DN (1976) Census techniques for seabirds of arctic and eastern Canada. Canadian Wildlife Service Occasional Paper 25. Canadian Wildlife Service Ottawa
Ratz H, Thompson C (1999) Who is watching whom? Checks for impacts of tourists on Yellow-eyed Penguins Megadyptes antipodes. Mar Ornithol 27:205–210
Seddon PJ, Davis LS (1989) Nest-site selection by Yellow-eyed Penguins. Condor 91:653–659
Seddon PJ, Ellenberg U, van Heezik Y (2011) Yellow-eyed penguins Megadyptes antipodes. In: Garcia-Borboroglu P, Boersma D (eds) Penguins: their conservation and management. Washington State University Press, Pullman (in press)
Smith KW, Ferns PN, Mudge GP (1981) Accuracy of nest counts at a mixed colony of herring and lesser black-backed gulls. Bird Study 28:244–248
Thomas L (1996) Monitoring long-term population change: why are there so many analysis methods? Ecology 77:49–58
Walter SE, Rusch DH (1997) Visibility bias on counts of nesting Canada geese. J Wildl Manag 61:768–772
Wanless S, Harris MP (1983) Effect of date on counts of nests of herring and lesser black-backed gulls. Ornis Scand 15:89–94
Williams BK, Nichols JD, Conroy MJ (2002) Analysis and management of animal populations. Academic Press, San Diego
Acknowledgments
We are grateful to the Department of Conservation (Coastal Otago) and to the Yellow-eyed Penguin Trust for supporting the project, for allocating the resources and the staff for one of the search teams and for making the previous years’ nest locations available. A special thank you to Melanie Young, Aviva Stein, Kate Beer, Cheryl Pullar, Dave McFarlane and Leith Thomson for their contribution to the project in the field and for their help with logistics. Kelly Buckle, Nicolas Dussex, Nicolas Fasel, Brendan Ford, Jim Fyfe, Lauren Kiff, Sarah Meadows, Riki Mules, Alice Thomas and Han Wolsink assisted with nest searches. Thank you to Murray Efford for feedback during the design stage of the experiment, and to two anonymous reviewers whose comments have improved our manuscript.
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Communicated by P. H. Becker.
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Hegg, D., Giroir, T., Ellenberg, U. et al. Yellow-eyed Penguin (Megadyptes antipodes) as a case study to assess the reliability of nest counts. J Ornithol 153, 457–466 (2012). https://doi.org/10.1007/s10336-011-0761-7
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DOI: https://doi.org/10.1007/s10336-011-0761-7