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Urban landscapes have a negative impact on bird species diversity, yet particular species thrive in urban communities. Like many other corvids, the Korean magpie is a successful colonizer of urban environments. On the semiurban campus of Seoul National University in Korea, we investigated whether magpies adjust territory size with building area and secondarily, whether they use vegetation and artificial components of their territory as indicators of prey density. We measured territorial areas and divided these into vegetation and artificial areas, distinguishing building area as a separate feature. We sampled prey density on each territory during the nestling stage. Territory size increased with the square root of building area (SRBA). As the length of building perimeter also increases with SRBA, we conclude that territory size was proportional to building perimeter. Prey density decreased with SRBA indicating that buildings had a negative impact on prey. Breeding success was also negatively related to SRBA. We suggest that magpies adjusted territory size according to the length of building perimeter due to a decline in prey density. As prey density declined, artificial pavement area was added to include open trash bins, which increase the availability of anthropogenic refuse such as discarded food. Vegetation area declined as prey density increased, but changes in vegetation area were minor and had little impact on prey availability measured at ground level. Structural cues were not used to adjust vegetation area, and artificial structural cues were not used to adjust territorial size over direct monitoring of prey density.
Site quality may influence breeding performance especially in raptors showing strong territory fidelity as predicted by the site-dependent population regulation hypothesis. Thus, the occupancy of nest-sites is non-random, indicating a preference of certain territories, apparently of higher quality. During four breeding seasons (2003-2006), we recorded the occupancy rate and the number of young fledged from Lanner Falcon Falco biarmicus feldeggii nest-sites in eastern Sicily, Italy. Breeding sites with different occupancy rates showed significant differences in environmental attributes, mainly altitude. A generalised linear model revealed a significant effect of the slope of the nest-site on mean fledgling number per successful pair. In addition, the mean slope of the nest territory and the slope of the nest-site are the main predictors for differentiating the cliff selection by Lanners and by much more competitive Peregrine Falcons Falco peregrinus. Finally, our results suggest a crucial role of the high quality sites for the population viability. Occupancy rates were positively related to the mean number of young fledged per territorial pair and during the four years of the study period six high quality nest-sites raised 58% of young produced in the whole study area. We suggest that the annual production of young of the high quality territories should be preserved and that evaluation of the effective contribution of the low quality sites for the persistence of a viable population in Sicily should be performed.
The authors correlated the percentage cover of forested areas with Tawny Owl Strix aluco density and territory size measured in deciduous woodlands along the elevation gradient in central Italy. They calculated the amount of wooded areas per owl territory on the basis of four forest types (urban woods, sclerophyllous woods, mesophilous woods, and montane beech woods). Breeding density differed 3-fold among forest types and suggests that wood quality has a direct effect in determining spatial patterns. The amount of wooded areas per territory is fairly stable in all forest types, and indicates a mean requirement of ca. 10 ha per territory. The smallest territories were in ca. 5 ha sized. Minimum habitat requirement may depend locally on wood quality. Management strategies based on the forest type should be undertaken to protect the local high-density populations of this owl.
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