Abstract
Estimating long-term population trends is vital for the conservation and management of species, yet few trends exist and fewer still are verified with independent measures. We compared three independent measures of change in population size over 27 years (1984–2011) for a significant Little Penguin Eudyptula minor colony in south-eastern Australia: (1) a series of 13 colony-wide surveys conducted in eight separate years, (2) mean nightly counts of penguins returning to breeding sites (365 counts × 27 years) and (3) population growth rates from a demographic model based on survival and recruitment rates measured at three sites each year. Colony-wide surveys of burrows were used as a benchmark of change in population size in the 8 years they were conducted as they were a robust measure of population size corrected for intra-annual variation in burrow occupancy using mark-recapture modelling at six reference sites. However, the demographic model matched the trend from colony-wide surveys with greater resolution in years and with less effort. Beach counts were unreliable for monitoring trends for the entire population due to its singular and peripheral location in the colony. Trends indicate a doubling of the population from 1984 to 2011 despite a marked population contraction linked to a mass mortality of a key prey species. The colony appears secure but remains subject to changes in the marine and terrestrial environments in the longer term.
References
Ainley DG, Hyrenbach KD (2010) Top-down and bottom-up factors affecting seabird population trends in the California current system (1985–2006). Prog Oceanogr 84(3–4):242–254. doi:10.1016/j.pocean.2009.10.001
Brothers N, Pemberton D, Pryor H, Halley V (2001) Tasmania’s Offshore Islands: seabirds and other natural features. Tasmanian Museum and Art Gallery, Hobart
Burnham KP, Anderson DR (2002) Model selection and multimodel inference: a practical information-theoretic approach, 2nd edn. Springer, New York
Chiaradia AF, Forero MG, Hobson KA, Cullen JM (2010) Changes in diet and trophic position of a top predator 10 years after a mass mortality of a key prey. ICES J Mar Sci 67:1710–1720
Clarke ED, Spear LB, McCracken ML, Marques FFC, Borchers DL, Buckland ST, Ainley DG (2003) Validating the use of generalized additive models and at-sea surveys to estimate size and temporal trends of seabird populations. J Appl Ecol 40(2):278–292. doi:10.1046/j.1365-2664.2003.00802.x
Dann P (1992) Distribution, population trends and factors influencing the population size of little penguins Eudyptula minor on Phillip Island, Victoria. Emu 91:263–272
Dann P (1994) The abundance, breeding distribution and nest sites of blue penguins in Otago, New Zealand. Notornis 41(3):157–166
Dann P, Norman FI (2006) Population regulation in little penguins (Eudyptula minor): the role of intraspecific competition for nesting sites and food during breeding. Emu 106(4):269–289
Dann P, Norman FI, Cullen JM, Neira FJ, Chiaradia A (2000) Mortality and breeding failure of little penguins, Eudyptula minor, in Victoria, 1995–96, following a widespread mortality of pilchard, Sardinops sagax. Mar Freshw Res 51(4):355–362
Development Core Team R (2011) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna
Fullagar PJ, Heyligers PC, Crowley MA, Klomp NI (1995) Gabo Island penguin survey, November 1994, vol 4. M. I. Partners, Moruya
Giling D, Reina RD, Hogg Z (2008) Anthropogenic influence on an urban colony of the little penguin Eudyptula minor. Mar Freshw Res 59(7):647–651. doi:10.1071/mf08003
Harris MP, Bode KG (1981) Populations of Little Penguins, Short-tailed Shearwaters and other seabirds on Phillip Island, Victoria, 1978. Emu 81:20–28
Harris MP, Norman FI (1981) Distribution and status of coastal colonies of seabirds in Victoria. Mem Natl Mus Vic 42:89–106
IUCN (2010) Guidelines for using the IUCN Red List categories and criteria.85
Laake J, Rakhimberdiev E, Collier B, Rotella J, Paul A (2012) RMark: R Code for MARK Analysis. R package version 2.1.3.
Link WA, Barker RJ (2005) Modeling association among demographic parameters in analysis of open population capture–recapture data. Biometrics 61(1):46–54
Marchant S, Higgins PJ (eds) (1990) Handbook of Australian, New Zealand and Antarctic birds, vol 1, Part A. Oxford University Press, Melbourne
McKechnie S, Fletcher D, Moller H, Scott DS, Newman J, Bragg C (2007) Estimating and correcting for bias in population assessments of Sooty Shearwaters. J Wildl Manage 71(4):1325–1335. doi:10.2193/2006-018
Montague TL (1982) The food and feeding ecology of Little Penguin Eudyptula minor at Phillip Island, Victoria, Australia. M.Sc. Thesis, Monash University, Clayton
Nicholls B (1918) An introduction to the study of the penguins on the Nobbies, Phillip Island, Western Port, Australia. Emu 17:118–144
Nisbet ICT, Dann P (2009) Reproductive performance of little penguins Eudyptula minor in relation to year, age, pair-bond duration, breeding date and individual quality. J Avian Biol 40(3):296–308. doi:10.1111/j.1600-048X.2008.04563.x
Possingham HP, Andelman SJ, Burgman MA, Medellín RA, Master LL, Keith DA (2002) Limits to the use of threatened species lists. Trends Ecol Evol 17(11):503–507
Pradel R (1996) Utilization of capture-mark-recapture for the study of recruitment and population growth rate. Biometrics 52:703–709
Rodrigues ASL, Pilgrim JD, Lamoreux JF, Hoffmann M, Brooks TM (2006) The value of the IUCN Red List for conservation. Trends Ecol Evol 21:71–76
Schwarz CJ, Arnason AN (1996) A general methodology for the analysis of capture-recapture experiments in open populations. Biometrics 52:860–873
Stevenson C, Woehler EJ (2007) Population decreases in Little Penguins Eudyptula minor in south-eastern Tasmania, Australia, over the past 45 years. Mar Ornithol 35(1):71–76
Stoklosa J (2012) Modern statistical methods for the analysis of capture-recapture data. PhD Dissertation, The University of Melbourne, Parkville
Sutherland DR, Dann P (2012) Improving the accuracy of population size estimates for burrow nesting seabirds. Ibis 154(3):488–498. doi:10.1111/j.1474-919X.2012.01234.x
Weerheim MS, Klomp NI, Brunsting AMH, Komdeur J (2003) Population size, breeding habitat and nest site distribution of little penguins (Eudyptula minor) on Montague Island, New South Wales. Wildl Res 30(2):151–157. doi:10.1071/wr02115
White GC, Burnham KP (1999) Program MARK: survival estimation from populations of marked animals. Bird Study 46(supplement):120–138
Wood SN (2011) Fast stable restricted maximum likelihood and marginal likelihood estimation of semiparametric generalized linear models. J Roy Stat Soc Ser B (Stat Method) 73(1):3–36
Yang HC, Chambers LE, Huggins RM (2005) A seasonal decomposition of the estimated size of a penguin population at Phillip Island, Australia. Aust J Zool 53(2):111–115. doi:10.1071/zo04014
Acknowledgments
We thank the many staff and volunteers that have collected data on penguin demographics, burrow occupancy and beach crossings over the years. Special mentions go to the Penguin Study Group, R. Jessop, L. Renwick, M. Healy, and P. Wasiak. Two anonymous reviewers helped improve earlier drafts of the manuscript. Procedures were undertaken under Phillip Island Nature Parks Animal Ethics Committee approvals and Department of Environment and Primary Industries Wildlife Use Permits.
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Sutherland, D.R., Dann, P. Population trends in a substantial colony of Little Penguins: three independent measures over three decades. Biodivers Conserv 23, 241–250 (2014). https://doi.org/10.1007/s10531-013-0597-y
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DOI: https://doi.org/10.1007/s10531-013-0597-y