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Has winter body condition varied with population size in a long-distance migrant, the Bewick’s Swan (Cygnus columbianus bewickii)?

  • Kevin A. Wood
  • Julia L. Newth
  • Geoff M. Hilton
  • Eileen C. Rees
Original Article

Abstract

Assessments of body condition can provide useful information on changes in the state of individuals within a population, which may in turn help to inform conservation efforts. For example, decreases in body condition over time can indicate reduced food resources. Mass and skull length measures recorded for 195 adult and 467 first winter (cygnets) Bewick’s Swans (Cygnus columbianus bewickii) at wintering sites in the UK between winters 1966/1967 and 2017/2018 therefore were analysed to determine whether a ca. 40% decline in numbers in the Northwest European Bewick’s Swan population between 1995 and 2010 corresponded with poorer body condition from the mid-1990s onwards. Parents and siblings were known for all individuals, allowing us to account for shared genetic factors and rearing environment in our analysis. We used linear mixed-effects models and an information-theoretic approach to test different models of temporal variation in scaled body mass index (SBMI). Within our study population, although SBMI values varied both within and between years, we found no evidence of any directional trends in body condition. Of our competing time models of swan SBMI, a model in which age-specific body condition was constant over time received the greatest support in the data. Body condition was greater for adults than cygnets, but did not vary between sexes or wintering sites. Our findings suggest no connection between the recent declines in population size and body condition. Population decline is therefore unlikely to be caused by inadequate food supplies.

Keywords

Animal biometrics Energy reserves Food resources Long-term ecological studies Species conservation Waterbirds Waterfowl demography 

Notes

Acknowledgements

This study would not have been possible without all of the WWT staff and volunteers who helped to capture and measure the Bewick’s Swans. We are grateful to all those who contributed to the co-ordinated international censuses of winter Bewick’s Swan numbers. We thank Robin Jones for assistance with data access, and Carl Mitchell, Dafila Scott, John Arbon and Linda Butler for information on site use by Bewick’s Swans. Thanks also to Christian Gortázar, an associate editor and anonymous reviewer for their helpful comments on an earlier version of this study. This study was funded by the Peter Scott Trust for Education and Research in Conservation, Peter Smith Charitable Trust for Nature, Olive Herbert Charitable Trust, D’Oyly Carte Charitable Trust, N. Smith Charitable Settlement, Robert Kiln Charitable Trust, the estate of the late Professor Geoffrey Matthews OBE and all who supported WWT’s ‘Hope for Swans’ appeal.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

References

  1. Albertsen JO, Abe Y, Kashikawa S, Ookawara A, Tamada K (2002) Age and sex differences in biometrics data recorded for whooper swans wintering in Japan. Waterbirds 25:334–339Google Scholar
  2. Armstrong DP, Ewen JG (2001) Testing for food limitation in reintroduced Hihi populations: contrasting results for two islands. Pac Conserv Biol 7:87–92CrossRefGoogle Scholar
  3. Armstrong DP, Perrott JK (2000) An experiment testing whether condition and survival are limited by food supply in a reintroduced Hihi population. Conserv Biol 14:1171–1181CrossRefGoogle Scholar
  4. Barton K (2012) MuMIn: model selection and model averaging based on information criteria. R package version 1.13.4Google Scholar
  5. Bates D, Mächler M, Bolker BM, Walker SC (2015) Fitting linear mixed-effects models using lme4. J Stat Softw 67:1–48CrossRefGoogle Scholar
  6. Bearhop S, Hilton GM, Votier SC, Waldron S (2004) Stable isotope ratios indicate that body condition in migrating passerines is influenced by winter habitat. Proc R Soc B 271(Suppl 4):S215–S218CrossRefPubMedGoogle Scholar
  7. BirdLife International (2015) European red list of birds. Office for Official Publications of the European Communities, LuxembourgGoogle Scholar
  8. Black JM, Rees EC (1984) The structure and behaviour of the whooper swan population wintering at Caerlaverock, Dumfries and Galloway, Scotland: an introductory study. Wildfowl 35:21–36Google Scholar
  9. Bolker BM, Brooks ME, Clark CJ, Geange SW, Poulsen JR, Stevens MHH, White JSS (2009) Generalized linear mixed models: a practical guide for ecology and evolution. Trends Ecol Evol 24:127–135CrossRefPubMedGoogle Scholar
  10. Bowler JM (1994) The condition of Bewick's swans Cygnus columbianus bewickii in winter as assessed by their abdominal profiles. Ardea 82:241–241Google Scholar
  11. Brazil M (2002) Brood amalgamation in Bewick’s swan Cygnus columbianus bewickii: a record from Japan. J Yamashina Inst Ornithol 33:204–209CrossRefGoogle Scholar
  12. Brown ME (1996) Assessing body condition in birds. In: Nolan V Jr, Ketterson ED (eds) Current ornithology. Springer, New York, pp 67–135CrossRefGoogle Scholar
  13. Brown DR, Sherry TW (2006) Food supply controls the body condition of a migrant bird wintering in the tropics. Oecologia 149:22–32CrossRefPubMedGoogle Scholar
  14. Burnham KP, Anderson DR (2004) Multimodel inference: understanding AIC and BIC in model selection. Sociol Methods Res 33:261–304CrossRefGoogle Scholar
  15. Burnham KP, Anderson DR, Huyvaert KP (2011) AIC model selection and multimodel inference in behavioral ecology: some background, observations, and comparisons. Behav Ecol Sociobiol 65:23–35CrossRefGoogle Scholar
  16. Burton NH, Rehfisch MM, Clark NA, Dodd SG (2006) Impacts of sudden winter habitat loss on the body condition and survival of redshank Tringa totanus. J Appl Ecol 43:464–473CrossRefGoogle Scholar
  17. Ciach M, Czyż S, Wieloch M (2018) Bill colour pattern in Bewick’s swan: information on sex and body size displayed on face? Ethol Ecol Evol 30:39–50CrossRefGoogle Scholar
  18. Dill HH, Thornsberry WH (1950) A cannon-projected net trap for capturing waterfowl. J Wildl Manag 14:132–137CrossRefGoogle Scholar
  19. Dirksen S, Beekman JH, Slagboom TH (1991) Bewick’s swans Cygnus columbianus bewickii in the Netherlands: numbers, distribution and food choice during the wintering season. Wildfowl (Supplement No. 1):228–237Google Scholar
  20. Eadie JM, Kehoe FP, Nudds TD (1988) Pre-hatch and post-hatch brood amalgamation in north American Anatidae: a review of hypotheses. Can J Zool 66:1709–1721CrossRefGoogle Scholar
  21. Evans ME (1979) Aspects of the life cycle of the Bewick’s swan, based on recognition of individuals at a wintering site. Bird Study 26:149–162CrossRefGoogle Scholar
  22. Evans ME (1982) Movements of Bewick’s swans, Cygnus columbianus bewickii marked at Slimbridge, England from 1960 to 1979. Ardea 70:59–75Google Scholar
  23. Evans ME, Kear J (1978) Weights and measurements of Bewick’s swans during winter. Wildfowl 29:118–122Google Scholar
  24. Griffin LR, Rees EC, Hughes B (2016) Satellite-tracking of Bewick’s swan migration in relation to offshore and onshore wind farm sites: final report to the Department of Energy and Climate Change. Wildfowl & Wetlands Trust, SlimbridgeGoogle Scholar
  25. Hoare JM, Pledger S, Keall SN, Nelson NJ, Mitchell NJ, Daugherty CH (2006) Conservation implications of a long-term decline in body condition of the Brothers Island tuatara (Sphenodon guntheri). Anim Conserv 9:456–462CrossRefGoogle Scholar
  26. Hurlbert SH (1984) Pseudoreplication and the design of ecological field experiments. Ecol Monogr 54:187–211CrossRefGoogle Scholar
  27. Kirby JS, Stattersfield AJ, Butchart SH, Evans MI, Grimmett RF, Jones VR, O’Sullivan J, Tucker GM, Newton I (2008) Key conservation issues for migratory land- and waterbird species on the world’s major flyways. Bird Conserv Int 18:S49–S73CrossRefGoogle Scholar
  28. Larsson K, Van der Jeugd HP, Van der Veen IT, Forslund P (1998) Body size declines despite positive directional selection on heritable size traits in a barnacle goose population. Evolution 52:1169–1184CrossRefPubMedGoogle Scholar
  29. Limpert RJ, Allan HA Jr, Sladen WJ (1987) Weights and measurements of wintering tundra swans. Wildfowl 38:108–113Google Scholar
  30. Luigujõe L, Kuresoo A, Keskpaik J, Ader A, Leito A (1996) Migration and staging of the Bewick’s swan (Cygnus columbianus) in Estonia. Gibier Faune Sauvage 13:451–461Google Scholar
  31. Mainguy J, Bêty J, Gauthier G, Giroux JF (2002) Are body condition and reproductive effort of laying greater snow geese affected by the spring hunt? Condor 104:156–161CrossRefGoogle Scholar
  32. McWilliams SR, Guglielmo C, Pierce B, Klaassen M (2004) Flying, fasting, and feeding in birds during migration: a nutritional and physiological ecology perspective. J Avian Biol 35:377–393CrossRefGoogle Scholar
  33. Meier-Peithmann W (2011) Dokumentation des nahrungsokologischen Wandels bei Sing-, Zwerg- und Hockerschwan Cygnus cygnus, C. bewickii, C. olor von 1965 bis 2010 in den Dannenberger Elbbogen. Vogelwelt 132:57–79 [In German with English summary]Google Scholar
  34. Monaghan P (2008) Early growth conditions, phenotypic development and environmental change. Philos Trans R Soc B 363:1635–1645CrossRefGoogle Scholar
  35. Morrison RIG, Davidson NC, Wilson JR (2007) Survival of the fattest: body stores on migration and survival in red knots Calidris canutus islandica. J Avian Biol 38:479–487CrossRefGoogle Scholar
  36. Nagy S, Petkov N, Rees EC, Solokha A, Hilton G, Beekman J, Nolet B (2012) International Single Species Action Plan for the Northwest European Population of Bewick’s Swan (Cygnus columbianus bewickii). AEWA Technical Series No 44, BonnGoogle Scholar
  37. Nakagawa S, Schielzeth H (2013) A general and simple method for obtaining R2 from generalized linear mixed-effects models. Methods Ecol Evol 4:133–142CrossRefGoogle Scholar
  38. Newth JL, Rees EC, Cromie RL, McDonald RA, Bearhop S, Pain DJ, Norton GJ, Deacon C, Hilton GM (2016) Widespread exposure to lead affects the body condition of free-living whooper swans Cygnus cygnus wintering in Britain. Environ Pollut 209:60–67CrossRefPubMedGoogle Scholar
  39. Newton I (2006) Can conditions experienced during migration limit the population levels of birds? J Ornithol 147:146–166CrossRefGoogle Scholar
  40. Newton I (2013) Bird populations. Harper Collins, LondonGoogle Scholar
  41. Nolet BA, Gyimesi A, Lith B (2014) Lower foraging efficiency of offspring constrains use of optimal habitat in birds with extended parental care. Ibis 156:387–394CrossRefGoogle Scholar
  42. Norambuena MC, Bozinovic F (2009) Health and nutritional status of a perturbed black-necked swan (Cygnus melanocoryphus) population: diet quality. J Zoo Wildl Med 40:607–616CrossRefPubMedGoogle Scholar
  43. Nowak E, Berthold P, Querner U (1990) Satellite tracking of migrating Bewick’s swans. Naturwissenschaften 77:549–550CrossRefGoogle Scholar
  44. Nuijten RJ, Kölzsch A, van Gils JA, Hoye BJ, Oosterbeek K, de Vries PP, Klaassen M, Nolet BA (2014) The exception to the rule: retreating ice front makes Bewick’s swans Cygnus columbianus bewickii migrate slower in spring than in autumn. J Avian Biol 45:113–122CrossRefGoogle Scholar
  45. O'Brien MF, Lee R, Cromie R, Brown MJ (2016) Assessment of the rates of injury and mortality in waterfowl captured with five methods of capture and techniques for minimizing risks. J Wildl Dis 52:S86–S95CrossRefPubMedGoogle Scholar
  46. Owen M, Cook WA (1977) Variations in body weight, wing length and condition of mallard Anas platyrhynchos platyrhynchos and their relationship to environmental changes. J Zool 183:377–395CrossRefGoogle Scholar
  47. Peig J, Green AJ (2009) New perspectives for estimating body condition from mass/length data: the scaled mass index as an alternative method. Oikos 118:1863–1891CrossRefGoogle Scholar
  48. Piersma T, Lindström Å (2004) Migratory shorebirds as integrative sentinels of global environmental change. Ibis 146:s61–s69CrossRefGoogle Scholar
  49. R Development Core Team (2016) R: a language and environment for statistical computing [3.3.0]. R Foundation for Statistical Computing, Vienna http://www.R-project.org/ Google Scholar
  50. Rees EC (1990) Bewick’s swans: their feeding ecology and coexistence with other grazing Anatidae. J Appl Ecol 27:939–951CrossRefGoogle Scholar
  51. Rees EC (2006) Bewick’s swan. T&AD Poyser, LondonGoogle Scholar
  52. Rees EC, Bacon PJ (1996) Migratory tradition in Bewick’s swans (Cygnus columbianus bewickii). Gibier Faune Sauvage 13:407–420Google Scholar
  53. Rees EC, Beekman JH (2010) Northwest European Bewick’s swans: a population in decline. Br Birds 103:640–650Google Scholar
  54. Rees EC, Bowler J (1996) Fifty years of swan research and conservation by the Wildfowl & Wetlands Trust. Wildfowl 47:248–263Google Scholar
  55. Scott P (1966) The Bewick’s swans at Slimbridge. Wildfowl 17:20–26Google Scholar
  56. Scott DK (1980) Functional aspects of prolonged parental care in Bewick’s swans. Anim Behav 28:938–952CrossRefGoogle Scholar
  57. Stevenson RD, Woods WA (2006) Condition indices for conservation: new uses for evolving tools. Integr Comp Biol 46:1169–1190CrossRefPubMedGoogle Scholar
  58. Stillman RA, Wood KA, Gilkerson W, Elkinton E, Black JM, Ward DH, Petrie M (2015) Predicting effects of environmental change on a migratory herbivore. Ecosphere 7:114CrossRefGoogle Scholar
  59. Warton DI, Duursma RA, Falster DS, Taskinen S (2012) Smatr 3—an R package for estimation and inference about allometric lines. Methods Ecol Evol 3:257–259 Accessible at https://CRAN.R-project.org/package=smatrCrossRefGoogle Scholar
  60. Wood KA, Stillman RA, Goss-Custard JD (2015) Co-creation of individual-based models by practitioners and modellers to inform environmental decision-making. J Appl Ecol 52:810–815CrossRefGoogle Scholar
  61. Wood KA, Newth JL, Hilton GM, Nolet BA, Rees EC (2016) Inter-annual variability and long-term trends in breeding success in a declining population of migratory swans. J Avian Biol 47:597–609CrossRefGoogle Scholar
  62. Wood KA, Ponting J, D’Costa N, Newth JL, Rose PE, Glazov P, Rees EC (2017) Understanding intrinsic and extrinsic drivers of aggressive behaviour in waterbird assemblages: a meta-analysis. Anim Behav 126:209–216CrossRefGoogle Scholar
  63. Wood KA, Nuijten RJM, Newth JL, Haitjema T, Vangeluwe D, Ioannidis P, Harrison AL, MacKenzie C, Hilton GM, Nolet BA, Rees EC (2018) Apparent survival of an Arctic-breeding migratory bird over 44 years of fluctuating population size. Ibis 160:413–430CrossRefGoogle Scholar
  64. Worden J, Cranswick PA, Crowe O, McElwaine G, Rees EC (2006) Numbers and distribution of Bewick’s swan Cygnus columbianus bewickii wintering in Britain and Ireland: results of international censuses, January 1995, 2000 and 2005. Wildfowl 56:3–22Google Scholar
  65. Zuur AF, Ieno EN, Elphick CS (2010) A protocol for data exploration to avoid common statistical problems. Methods Ecol Evol 1:3–14CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Wildfowl & Wetlands TrustGloucestershireUK

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