Raptors are still affected by environmental pollutants: Greenlandic Peregrines will not have normal eggshell thickness until 2034

Knud Falk 1 , Søren Møller 2 , Frank F. Rigét 3 , Peter B. Sørensen 4 ,  and Katrin Vorkamp 5
  • 1 , Stockholm, Sweden
  • 2 Roskilde University Library, , 4000, Roskilde, Denmark
  • 3 Aarhus University, Danish Centre for Environment and Energy, Arctic Research Centre, Department of Bioscience, 4000, Roskilde, Denmark
  • 4 Aarhus University, Danish Centre for Environment and Energy, Department of Bioscience, 8600, Silkeborg, Denmark
  • 5 Aarhus University, Danish Centre for Environment and Energy, Arctic Research Centre, Department of Environmental Science, Roskilde, Denmark


The DDT-induced effects, eggshell thinning and breeding failure in Peregrine Falcon (Falco peregrinus) populations were reverted with restrictions on the use of the compound from the 1970s, and in most studied populations, the eggshell thickness is back to normal. In Greenland, a previous study of eggshell thinning in Peregrines found that shells had not yet reached pre-DDT levels. In this study, we extend the time series and reinterpret shell thinning data for 196 clutches covering a 45-year time span (1972–2017). There was a significant (P<0.001) increase in the eggshell thickness of 0.23% per year. This corresponds to a change in eggshell thinning from 14.5% to 5.4% in 2017 compared to the pre-DDT mean. With the current rate of change, pre-DDT shell thickness is predicted to be reached around the year 2034. However, a few clutches are still below the critical limit. The relatively slower recovery of the shell thickness in the Greenland population is likely indicative of the slower phasing out of DDT in the Greenlandic Peregrines’ wintering grounds in Latin America. The shell thinning in the Greenlandic population probably never crossed the 17% threshold associated with population declines, contrary to the populations in many other parts of the world.

If the inline PDF is not rendering correctly, you can download the PDF file here.

  • AMAP 2016. AMAP Assessment 2015: Temporal Trends in Persistent Organic Pollutants in the Arctic. – Arctic Monitoring and Assessment Programme (AMAP), Oslo, Norway. vi+71pp

  • Bennett, R. S. 1995. Relative sensitivity of several measures of eggshell quality to the stage of embryonic development. – Bulletin of Environmental Contamination and Toxicology 54: 428–431. DOI: 10.1007/BF00195116

  • Bunck, C. M., Spann, J. W., Pattee, O. H. & Fleming, W. J. 1985. Changes in eggshell thickness during incubation: implications for evaluating the impact of organochlorine contaminants on productivity. – Bulletin of Environmental Contamination and Toxicology 35: 173–182. DOI:10.1007/BF01636496

  • Burnham, W. A. & Mattox, W. G. 1984. Biology of the Peregrine and Gyrfalcon in Greenland. – Meddelelser om Grønland, Bioscience 14: 1–25.

  • Cade, T., Enderson, J., Thelander, C. & White, C. (eds.) 1988. Peregrine Falcon populations – their management and recovery. – The Peregrine Fund, Idaho

  • Castilla, A. M., Herrel, A., Robles, H., Malone, J. & Negro, J. J. 2010. The effect of developmental stage on eggshell thickness variation in endangered falcons. – Zoology 113: 184–188. DOI: 10.1016/j.zool.2009.10.002

  • Falk, K. & Møller, S. 1988. Status of the Peregrine Falcon in South Greenland: Population Density and Reproduction. – In: Cade, T. J., Enderson, J. H., Thelander, C. G. & White, C. M. (eds.) Peregrine Falcon Populations: Their Management and Recovery. – The Peregrine Fund, Boise, pp. 37–43.

  • Falk, K. & Møller, S. 1990. Clutch Size Effects on Eggshell Thickness in the Peregrine Falcon and European Kestrel. – Ornis Scandinavica 21: 265. DOI: 10.2307/3676390

  • Falk, K. & Møller, S. 2018. Field Report 2018. Monitoring of the Peregrine Falcon population in South Green-land. – http://vandrefalk.dk/feltrap/rap2018.pdf

  • Falk, K., Møller, S. & Mattox, W. G. 2006. A long-term increase in eggshell thickness in Greenlandic Peregrine Falcons Falco peregrinus tundrius. – Science of Total Environment 355: 127–134. DOI: 10.1016/j.scitotenv.2005.02.024

  • Hickey, J. J. 1969. Peregrine Falcon Populations, their Biology and Decline. – University of Wisconsin Press, Madison & London

  • Mattox, W. & Seegar, W. 1988. The Greenland Peregrine Peregrine Falcon survey, 1972–1985, with emphasis on recent population status. – In: Cade, T. J., Enderson, J. H., Thelander, C. G. & White, C. M. (eds.) Peregrine Falcon Populations: Their Management and Recovery. – The Peregrine Fund, Boise, pp. 27–36.

  • Newton, I. 1979. Population ecology of raptors. – T & AD Poyser, Berkhamstead

  • Odsjö, T. & Sondell, J. 1982. Eggshell thinning and DDT, PCB and mercury in eggs of Osprey (Pandion haliaetus (L.)) in Sweden and their relations to breeding success. – In: Odsjö, T. (ed.) Eggshell Thickness and Levels of DDT, PCB and Mercury in Eggs of Osprey (Pandion Haliaetus (L.)) and Marsh Harrier (Circus aeruginosus (L.)) in Relation to Their Breeding Success and Population Status in Sweden. – Thesis (Doctoral), University of Stockholm, 1982. – GOTAB, Stockholm

  • Odsjö, T. & Sondell, J. 2014. Eggshell thinning of Osprey (Pandion haliaetus) breeding in Sweden and its significance for egg breakage and breeding outcome. – Science of Total Environment 470–471: 1023–1029. DOI: 10.1016/j.scitotenv.2013.10.051

  • Peakall, D. B. & Kiff, L. F. 1988. DDE contamination in Peregrines and American Kestrels and its effect on reproduction. – In: Cade, T. J., Enderson, J. H., Thelander, C. G. & White, C. M. (eds.) Peregrine Falcon Populations: Their Management and Recovery. – The Peregrine Fund, Boise, pp. 337–350.

  • R Core Team 2015. R: A language and environment for statistical computing. – R Foundation for Statistical Computing, Vienna, Austria. URL http://www.R-project.org/

  • Ratcliffe, D. A. 1970. Changes Attributable to Pesticides in Egg Breakage Frequency and Eggshell Thickness in Some British Birds. – Journal of Applied Ecology 7: 67–115. DOI: 10.2307/2401613

  • Rigét, F., Vorkamp, K., Bossi, R. Sonne, C., Letcher, R. J. & Dietz, R. 2016. Twenty years of monitoring of persistent organic pollutants in Greenland biota. A review. – Environmental Pollution 217: 114–123.

  • UNEP 2009. Stockholm Convention on Persistent Organic Pollutants, as amended in 2009. – text and annexes. www.pops.int

  • Vorkamp, K., Falk, F., Møller, S., Rigét, F. F., Bossi, R. & Sørensen, P. B. 2017. New and updated time trends of persistent organic pollutants and their effects on eggs of Peregrine Falcons (Falco peregrinus) from South Greenland. – Aarhus University, DCE – Danish Centre for Environment and Energy, pp. 80, Scientific Report from DCE – Danish Centre for Environment and Energy No. 249 http://dce2.au.dk/pub/SR249.pdf

  • Vorkamp, K., Falk, K., Møller, S., Rigét, F. & Sørensen, P. 2018. Regulated and unregulated halogenated flame retardants in Peregrine Falcon eggs from Greenland. – Environmental Science & Technology 52: 474–483. DOI: 10.1021/acs.est.7b04866

  • Vorkamp, K., Thomsen, M., Møller, S., Falk, K. & Sørensen, P. B. 2009. Persistent organochlorine compounds in Peregrine Falcon (Falco peregrinus) eggs from South Greenland: Levels and temporal changes between 1986 and 2003. – Environment International 35: 336–341. DOI: 10.1016/j.envint.2008.08.008

  • Wegner, P., Kleinstäuber, G., Baum, F. & Schilling, F. 2005. Long-term investigation of the degree of exposure of German Peregrine Falcons (Falco peregrinus) to damaging chemicals from the environment. – Journal of Ornithology 146: 34–54. DOI: 10.1007/s10336-004-0053-6


Journal + Issues