ESTONIAN ACADEMY
PUBLISHERS
eesti teaduste
akadeemia kirjastus
cover
Estonian Journal of Ecology
Numbers and hybridization of spotted eagles in Estonia as revealed by country-wide field observations and genetic analysis; pp. 143–154
PDF | doi: 10.3176/eco.2011.2.05

Author
Ülo Väli
Abstract
Spotted eagles include two medium-sized similar raptors breeding sympatrically in Estonia. In the current study I checked if population numbers derived from country-wide field observations over a 20-year period were in line with the estimate extrapolated from surveys in study plots (500–600 breeding territories of the Lesser Spotted Eagle and 10–30 territories of the Greater Spotted Eagle). I also analysed the structure of the hybridizing spotted eagle population using field descriptions and genetic analysis. The country-wide census enabled to distinguish 664 putative breeding territories, in 81% of which eagles were recorded in two or more years while in 53% breeding was confirmed. In 492 territories the species was identified in the field from morphological characters, and in 158 of them genetic analysis was used to verify the identification. The Greater Spotted Eagle was observed in 26 territories, in 54% of which breeding was confirmed. Altogether 10 pure-species Greater Spotted Eagle pairs and 14 pairs mixed with the Lesser Spotted Eagle were recorded whereas in 12 territories species compositions changed – mainly towards hybridization and Lesser Spotted Eagle pairs. Genetic analysis suggested breeding of an adult hybrid spotted eagle in eight territories and later generation backcrosses in five territories. The present study supported the plot-based estimates of population size but also showed extensive, partly hidden hybridization and decline of the Greater Spotted Eagle. It also showed that, despite several caveats, full census based on a large database of casual field observations can be a powerful tool for estimating the size and distribution of a rather numerous raptor population and is essential for discovering breeding sites of a rare species. In hybridizing species, however, more specialized approaches (comprehensive search of nests, detailed morphological descriptions, and genetic analysis) should be used as well.
References

Allendorf, F. W., Leary, R. F., Spruell, P. & Wenburg, J. K. 2001. The problems with hybrids: setting conservation guidelines. Trends Ecol. Evol., 16, 613–622.
doi:10.1016/S0169-5347(01)02290-X

Bergmanis, U. 1996. On the taxonomy of the lesser spotted eagle Aquila pomarina and greater spotted eagle A. clanga. In Eagle Studies (Meyburg, B.-U. & Chancellor, R. D., eds), pp. 199–207. WWGBP, Berlin.

Bibby, C. J., Burgess, N. D. & Hill, D. A. 2000. Bird Census Techniques. Academic Press, London.

BirdLife International. 2004. Birds in Europe: Population Estimates, Trends and Conservation Status. BirdLife International, Cambridge, UK.

Coyne, J. A. & Orr, H. A. 2004. Speciation. Sinauer Associates Inc, Sunderland.

Cramp, S. & Simmons, K. E. L. 1980. The Birds of the Western Palearctic. Vol. 2. Oxford University Press, Oxford.

Dombrovski, V. C. 2006. Morphological characteristics and diagnostic features of the Greater Spotted (Aquila clanga), Lesser Spotted (A. pomarina) eagles, and their hybrids. Ornitologia, 33, 29–41.

Elts, J., Kuresoo, A., Leibak, E., Leito, A., Lilleleht, V., Luigujõe, L., Lõhmus, A., Mägi, E. & Ots, M. 2003. Eesti lindude staatus, pesitsusaegne ja talvine arvukus 1998.–2002. a. Hirundo, 16, 58–83.

Elts, J., Kuresoo, A., Leibak, E., Leito, A., Leivits, A., Lilleleht, V., Luigujõe, L., Mägi, E., Nellis, R., Nellis, R. & Ots, M. 2009. Eesti lindude staatus, pesitsusaegne ja talvine arvukus 2003–2008. Hirundo, 22, 3–31.

Forsman, D. 1999. The Raptors of Europe and the Middle East: A Handbook of Field Identification. Poyser, London.

Gregory, R. D., Gibbons, D. W. & Donald, P. F. 2004. Bird census and survey techniques. In Bird Ecology and Conservation. A Handbook of Techniques (Sutherland, W. J., Newton, I. & Green, R. E., eds), pp. 17–55. Oxford University Press, Oxford.
doi:10.1093/acprof:oso/9780198520863.003.0002

Hardey, J., Crick, H., Wernham, C., Riley, H., Etheridge, B. & Thompson, D. 2009. Raptors: A Field Guide for Surveys and Monitoring. Second edition. Scottish National Heritage, Edinburgh.

Härms, M. 1927. Eesti linnustik. Loodus, Tartu.

Kenward, R. E., Walls, S. S., Hodder, K. H., Pahkala, M., Freeman, S. N. & Simpson, V. R. 2000. The prevalence of non-breeders in raptor populations: evidence from rings, radio-tags and transect surveys. Oikos, 91, 271–279.
doi:10.1034/j.1600-0706.2000.910207.x

Kumari, E. 1954. Eesti NSV linnud. Eesti Riiklik Kirjastus, Tallinn.

Lepiksaar, J. & Zastrov, M. 1963. Die Vögel Estlands. Annales Societatis Tartuensis Ad Res Naturae Investigandas Constitutae, 3, 5–168.

Lilleleht, V. & Leibak, E. 1993. List, status and numbers of Estonian birds. Hirundo, 1993, 3–50.

Lint, J., Noon, B., Anthony, R., Forsman, E., Raphael, M., Collopy, M. & Starkey, E. 1999. Northern Spotted Owl Effectiveness Monitoring Plan for the Northwest Forest Plan. General technical report PNW-GTR-440. U.S. Department of Agriculture Forest Service, Portland.

Lõhmus, A. 1996. Segadus suur-konnakotkaga. Eesti Loodus, 1996, 228–230.

Lõhmus, A. 1998. The numbers of the Lesser Spotted Eagle and Greater Spotted Eagle in Estonia. Hirundo, 11, 24–34.

Lõhmus, A. & Väli, Ü. 2001. Numbers and population dynamics of the Lesser Spotted Eagle Aquila pomarina in Estonia. Acta Ornithoecologica, 4, 291–295.

Lõhmus, A. & Väli, Ü. 2004. The effects of habitat quality and female size on the productivity of the lesser spotted eagle Aquila pomarina in the light of the alternative prey hypothesis.
J. Avian Biol., 35, 455–464.
doi:10.1111/j.0908-8857.2004.03228.x

Lõhmus, A. & Väli, Ü. 2005. Habitat use by the vulnerable greater spotted eagle Aquila clanga interbreeding with the lesser spotted eagle A. pomarina in Estonia. Oryx, 39, 170–177.

Lontkowski, J. & Maciorowski, G. 2010. Identification of juvenile Greater Spotted Eagle, Lesser Spotted Eagle and hybrids. Dutch Birding, 32, 384–397.

Mänd, R. 1992. Eesti ornitoloogiline kirjandus muutuvas ajas. Eesti Loodus, 1992, 505–506.

Meyburg, B.-U., Haraszthy, L., Strazds, M. & Schäffer, N. 2001. European species action plans for Greater and Lesser Spotted Eagles. In European Union Action Plans for Eight Priority Bird Species (Schäffer, N. & Gallo-Orsi, U., eds). European Commission, Luxembourg.

Meyburg, B.-U., Belka, T., Danko, S., Wójciak, J., Heise, G., Blohm, T. & Matthes, H. 2005. Geschlechtsreife, Ansiedlungsentfernung, Alter und Todesursachen beim Schreiadler Aquila pomarina. Limicola, 19, 153–179.

Newton, I. 1985. The Sparrowhawk. Poyser, Calton.

Newton, I. & Rothery, P. 2001. Estimation and limitation of numbers of floaters in a Eurasian Sparrowhawk population. Ibis, 143, 442–449.
doi:10.1111/j.1474-919X.2001.tb04945.x

Price, T. 2008. Speciation in Birds. Roberts & Co, Greenwood.
Randla, T. 1976. Eesti röövlinnud. Valgus, Tallinn.

Randla, T. 1985. The present state of birds of prey in Estonia. Communications of the Baltic Commission for the Study of Bird Migration, 18, 41–47.

Randla, T. & Õun, A. 1983. On the density of the diurnal raptors and the eagle owl in Estonia. In Tezisy Dokladov 11 Pribaltijskoj Ornitologicheskoj Konferentsii, pp. 182–183. Tallinn (in Russian).

Renno, O. 1974. Fifty years of ornithofaunistic studies in Estonia. Ornitoloogiline kogumik, 7, 29–37.

Renno, O. 1993. Eesti linnuatlas. Valgus, Tallinn.

Rudnick, J. A., Katzner, T. E., Bragin, E. A., Rhodes, O. E. & Dewoody, J. A. 2005. Using naturally shed feathers for individual identification, genetic parentage analyses, and population monitoring in an endangered eastern imperial eagle (Aquila heliaca) population from Kazakhstan. Mol. Ecol., 14, 2959–2967.
doi:10.1111/j.1365-294X.2005.02641.x

Saurola, P. 1986. The raptor grid: an attempt to monitor Finnish raptors and owls. Vår Fågelvärld Suppl., 11, 187–190.

Scheller, W., Bergmanis, U., Meyburg, B.-U., Furkert, B., Knack, A. & Röper, S. 2001. Raum-Zeit-Verhalten des Schreiadlers (Aquila pomarina). Acta Ornithoecologica, 4, 75–236.

Schwartz, M. K., Luikart, G. & Waples, R. S. 2007. Genetic monitoring as a promising tool for conservation and management. Trends Ecol. Evol., 22, 25–33.
doi:10.1016/j.tree.2006.08.009

Steenhof, K. & Newton, I. 2007. Assessing nesting success and productivity. In Raptor Research and Management Techniques (Bird, D. M. & Bildstein, K. L., eds), pp. 181–192. Hancock House, Surrey.

Svensson, L., Mullarney, K., Zetterström, D. & Grant, P. J. 1999. Collins Bird Guide. HarperCollins, London.

Tammur, E. 1994. Lesser Spotted Eagle. In Birds of Estonia. Status, Distribution & Numbers (Leibak, E., Lilleleht, V. & Veromann, H., eds), p. 80. Estonian Academy Publishers, Tallinn.

Väli, Ü. 2002. Mitochondrial pseudo-control region in old world eagles (genus Aquila). Mol. Ecol., 11, 2189–2194.
doi:10.1046/j.1365-294X.2002.01578.x

Väli, Ü. 2003. The Lesser Spotted Eagle and its conservation in Estonia. Hirundo Suppl., 6, 1–66.

Väli, Ü. 2005. Hybridisation: a threat to European Greater Spotted Eagles Aquila clanga. In International Meeting on Spotted Eagles (Aquila clanga, A. pomarina and A. hastata) – Research and Conservation (Mizera, T. & Meyburg, B.-U., eds), pp. 103–114. Biebrzański Park Narodowy, Osowiec.

Väli, Ü. & Lõhmus, A. 2000. The Greater Spotted Eagle and its conservation in Estonia. Hirundo Suppl., 6, 1–50.

Väli, Ü. & Lõhmus, A. 2004. Nestling characteristics and identification of the Lesser Spotted Eagle Aquila pomarina, Greater Spotted Eagle A. clanga, and their hybrids. J. Ornithol., 145, 256–263.

Väli, Ü., Treinys, R. & Lõhmus, A. 2004. Geographical variation in macrohabitat use and preferences of the Lesser Spotted Eagle Aquila pomarina. Ibis, 146, 661–671.
doi:10.1111/j.1474-919x.2004.00300.x

Väli, Ü., Dombrovski, V., Treinys, R., Bergmanis, U., Daroczi, S. J., Dravecky, M., Ivanovski, V., Lontkowski, J., Maciorowski, G., Meyburg, B.-U., Mizera, T., Zeitz, R. & Ellegren, H. 2010a. Widespread hybridization between the Greater Spotted Eagle Aquila clanga and the Lesser Spotted Eagle A. pomarina (Aves: Accipitriformes) in Europe. Biol. J. Linn. Soc., 100, 725–736.
doi:10.1111/j.1095-8312.2010.01455.x

Väli, Ü., Saag, P., Dombrovski, V., Meyburg, B.-U., Maciorowski, G., Mizera, T., Treinys, R. & Fagerberg, S. 2010b. Microsatellites and single nucleotide polymorphisms in avian hybrid identification: a comparative case study. J. Avian Biol., 41, 34–49.
doi:10.1111/j.1600-048X.2009.04730.x

Väli, Ü., Männik, R., Nellis, R., Sein, G. & Tuvi, J. 2011. Eesti kotkaste seire – näiteid haruldaste liikide staatuse ja arvukuse määramisest. Eesti Loodusuurijate Seltsi Aastaraamat, 86, 92–106.

Volke, V. 1996. The status of the Greater Spotted Eagle Aquila clanga and Lesser Spotted Eagle A. pomarina in Estonia. In Eagle Studies (Meyburg, B.-U. & Chancellor, R. D., eds), pp. 285–289. WWGBP, Berlin.
Back to Issue

Back issues