EFFECTS OF BREEDING EXPERIENCE ON NEST-SITE CHOICE AND THE REPRODUCTIVE PERFORMANCE OF TAWNY OWLS (STRIX ALUCO)

摘要

Nest boxes for breeding Tawny Owls (Strix aluco) were located in a mixed oak-hornbeam-beech (Quercus—Carpinus—Fagus) forest located in the Duna-Ipoly National Park, 30 km northwest of Budapest, Hungary, during the period 1992-2004. We marked the parents individually in the first known breeding year of the females and recorded their reproductive performances through 5 subsequent breeding years. Reproductive performance of females increased with increasing breeding experience; they laid more eggs andreared more fledglings with subsequent breeding years. However, no significant differences were found in reproductive performance between the third and fifth breeding years. Fledging success was higher when the males were older than the females, but hatching success was not influenced by the age of the males. Parents achieved higher hatching and fledging success in years without snow cover than those with snow cover. Fledging success was higher than hatching success in the females' first and second breeding years, but hatching success was higher in third, fourth, and fifth breeding years, which indicates age-dependent change in offspring production limitation by parents. Pairs changed nest sites and moved to lower altitudes in years with snow. As a consequence, the majority of older parents bred at low elevations. Based on the greater mass loss by females than males in adverse weather conditions, we concluded that males reduced the amount of prey brought to their mates to ensure their own survival inconditions in which food was scarce. Females raised lighter fledglings in snow years than in years without snow cover during their first and second breeding season, but the influence of snow cover on fledglings' condition was not present in the broods of experienced parents.