Carlo Violani

Feeding ecology of the tawny owls (Strix aluco) in urban habitats (northern Italy)

Abstract From October 1986 through September 1989, the diet of tawny owls Strix aluco in the city of Pavia (northern Italy) was studied by examining 769 pellets coming from 4 pellet‐dropping stations. The results show that the owls fed mainly on birds (61.1% in biomass), whereas mammals accounted for 37%. Arthropods, especially ants, were numerous in the diet, mainly during summer although their biomass was slight. Seasonal changes in diet occurred throughout the year. During winter, the owls preyed on birds and mammals in the same proportions. Birds largely predominated in spring and sum mer, while mammals slightly prevailed in autumn. The diet of dif ferent individual tawny owls was quite similar qualitatively, but dif fered quantitatively, according to the habitats included in their respective territories.

Observations on the dynamics of Rutilus rubilio Cyprinidae in a man‐made hypertrophic basin (Arancio Lake, southwest Sicily)

Abstract Rutilus rubilio, recently introduced into Sicily, is now widespread in many man‐made basins and watercourses of the island. We investigated a population living in a man‐made hypertrophie basin of southwest Sicily (Lake Arancio) in 1995. Sampling was monthly by a trawl and trammel net. Morphometric and meristic features were taken, and sagittal otoliths were extracted to assess age. R. rubilio represented the dominant species in the fish community of the man‐made basin. The population was characterized by a slower isometric growth, as related to age, than the population of South Italy. Rutilus rubilio became naturalised successfully and has contributed in altering the composition of the fish community described in 1977 by Faranda.