Age-related territory occupation and fledgling production of males in a Central-European local population of tawny owls, Strix aluco

Sasvári, Lajos; Hegyi, Zoltán

Age-related territory occupation and fledgling production of males in a Central-European local population of tawny owls, Strix aluco

2011

Sasvári, Lajos | Hegyi, Zoltán

Nest boxes for breeding tawny owls (Strix aluco) were located in a mixed oak-hornbeam-beech (Quercus-Carpinus-Fagus) forest in the Duna-Ipoly National Park, 30 km northwest of Budapest, Hungary during the period 1992–2010. The 550 m altitude range (120–680 m) of the study area was divided into low and high elevations: < 400 m, and > 400 m, each containing 88 nest-boxes. We marked 77 males in their first breeding year and evaluated the lifetime territory occupation and reproductive performance for individuals which reached five, six, seven, eight or nine years old. The fledgling production of tawny owl males increased in their first, second and third years, reached a high level in years four and five, but declined once they were six years old. The relative low reproductive performance in the early and late years of the males' lives may be attributed to the fact that the majority of males were unable to occupy high quality territories, and the rate at which individuals skipped breeding was high. We suggest that both the reduced ability to acquire high quality territories and declining fledging production in late years of males reflect senescence patterns in tawny owls.

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