Age Structure of the Long-Eared Owl (Asio otus) Migration at Bukowo-Kopań Station (Southern Baltic Coast) in Autumns 1996-2003
Over 2000 Long-eared Owls were caught (217 adult and 1827 immatures) at Bukowo-Kopań station (54°21'N, 16°17'E / 54°28'N, 16°25'E), in the central part of the Polish Baltic coast, during autumn seasons 1996-2003. Migration of this species had wave-like pattern with three distinguished passage waves. There were differences between young and adult birds passage in subsequent passage waves (statistically significant only in autumns 2000 and 2003, in other seasons they were non-significant. The value of X2-test calculated for all seasons together was high and differences were significant (X2 = 10.96, p < 0.01). Generally, very high variation must be stressed. Young birds dominated during autumn migration (on average they constituted 89%) but this number varied distinctly in different years. The immatures were the most numerous in the second and third wave (they were especially numerous in the third wave in years with the highest number of caught birds). Adult owls migrated a bit earlier - average passage data was earlier by 1 to 16 days in various seasons. All data point at very high variability of the Long-eared Owl migration and necessity of deeper studies on this phenomenon.
Belopolsky L. 1974. Migration peculiarities of some species of owls (Strigiformes) on the basis of trapping and ringing data obtained on the Courland Spit in 1957-1968. Commun. Baltic Comm. Stud. Bird Migr. 8: 51-71.
Bengtsson D., Jonzen N. 2001. Autumn migration of Montagu's Harrier Circus pygargus and Marsh Harrier C. aeruginosus at the southern tip of Oland. Ornis Svecica 11, 1-2: 1-6.
Busse P. 1969. Results of ringing of European Corvidae. Acta orn. 11, 8: 263-328.
Busse P., Busse W. 2003. Autumn migration of owls along Polish Baltic coast 1961-1999. Vogelwelt 124, 6: 281-284.
Busse P., W. Kania 1970. Operation Baltic 1961-1967. Working methods. Acta orn. 12, 7: 251-267.
Cramp, Simmons, K.E.L. (Eds). 1985. The Birds of the Western Palearctic. Handbook of the Birds of Europe, the Middle East and North Africa. vol. 4. Oxford Univ. Press, Oxford.
Dobrynina I.N. 1994. Seasonal movements of owls (Strigiformes) in the Baltic region based on ringing data. Ring 16, 1-2: 77-83.
Glue D., Nilsson I.N. 1997. Long-eared Owl. In: Hagemeijer W.J.M. and Blair M.J. (Eds). The EBCC Atlas of European Breeding Birds: their Distribution and Abundance. T & A D Poyser, London: pp. 416-417.
Gromadzka J., Serra L. 1998. Differential migration of juvenile and adult Grey Plovers Pluvialis squatarola at the mouth of the Vistula River, Poland. Ornis Fenn. 75: 193-199.
Harvey P.V., Riddiford N. 1990. An uneven sex ratio of migrant Long-eared Owls. Ring. & Migr. 11: 132-135.
Kjellen N. 1998. Annual variation in numbers, age and sex ratios among migrating raptors at Falstebo, Sweden from 1986-1995. J. Ornithol. 139: 157-171.
Kjellen N. 1999. Different migration strategies among Swedish Common Buzzards Buteo buteo revealed by the proportion of white birds. Ornis Svecica 9, 1-2: 11-18.
Krupa R. 1997. Phenology and dynamics of autumn migration of Grey Plover (Pluvialis squatarola) through the Gulf of Gdańsk in years 1984-1995. Ring 19, 1-2: 93-104.
Meissner W. 1996. Timing and phenology of autumn migration of Common Sandpiper (Actitis hypoleucos) at the Gulf of Gdańsk. Ring 18, 1-2: 59-72.
Meissner W. 1997. Autumn migration of Wood Sandpiper (Tringa glareola) in the region of the Gulf of Gdańsk. Ring 19, 1-2: 75-91.
Meissner W., Koziróg L. 2000. Autumn migration of the Turnstone Arenaria interpres at the Bay of Gdańsk. Not. Orn. 41, 3: 213-223.
Meissner W., Ściborski M. 2002. Autumn migration of the Bar-tailed Godwit (Limosa lapponica) in the Gulf of Gdańsk region. Ring 24, 1:3-15.
Michalonek D., Busse W., Busse P. 2004. Seasonal migration pattern of owls at Bukowo-Kopań station (N Poland) in 2000-2003. Ring 26, 1:13-21.
Mikkola H. 1983. Owls of Europe. Buteo Books, Vermillion, South Dakota: pp. 211-232.
Payevsky V.A. 1998. Age structure of passerine migrants at the eastern Baltic coast: the analysis of the "coastal effect". Ornis Svecica 8, 4: 171-178.
Scott D. 1997. The Long-eared Owl. The Zoological Society of London.
Urcun J.R., Kabouche B. 2003. La migration postnuptiale du Circaete Jean-le-blanc Circaetus gallicus a travers les Pyrenees. Alauda 71, 2: 119-132.
Virkkala R. 1992. Fluctuations of vole-eating birds of prey in northern Finland. Ornis Fenn. 69, 2: 97-100.
Vogrin M. 1997. Occurrence and passage of Marsh Harrier (Circus aeruginosus), Hen Harrier (Circus cyaneus) and Osprey (Pandion haliaetus) in northeastern Slovenia. Ring 19, 1-2: 59-63.