Ardea
Official journal of the Netherlands Ornithologists' Union

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Orell M. & Ojanen M. (1979) Mortality rates of the Great Tit Parus major in a northern population. ARDEA 67 (3-4): 130-133
Annual mortality rates of Great Tits were estimated on the basis of 4,002 fledglings ringed in the Oulu area (65N. 25 E), northern Finland in 1968-77. From these birds 163 specimens were recaptured in the area as breeders in later years, and 44 specimens were recovered by the Finnish Ringing Centre after their first January of life. The age distribution of these birds is given in Table 1. The male Great Tits showed a lower mortality rate (48.7-54.9%) than did the females (51.7-55.2%; Table 1), although the difference between sexes seemed to be smaller than in populations further south (Table 3). The overall mortality of the adults is perhaps slightly greater in Oulu than in populations of central and Western Europe. The mortality among young birds up to their first breeding is about the same or even smaller (78.1 %) in Oulu as in Oxford and Oranje Nassau Oord, Netherlands. The reason for the mortality becoming heavier in Oulu than elsewhere after the first breeding season is perhaps predation in winter, which especially acts upon old individuals, and a long-term stress of hard climate.


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