Domestic cats are the most numerous predators in Poland. They are commonly kept at farms but hardly controlled, so penetrate freely wide range of habitats. The work aimed at determining the range of greatest impact of cats by identifying patterns of their activity and area searching, over daily, monthly and annual cycles. The density index, estimated from transect counts, performed along standard routes, proved to be dependent on temperature, precipitation and time of the day. In spring and summer, cats presented a two-peaked activity pattern, while in cold seasons it was more stable throughout the day. In warm months cats were registered at a further distance from the buildings than in colder ones. The animals were much less active when rain was falling. Cats’ responses on noticing an observer showed that the further they were from the edges of settlements the more timid and cautious they became. The results showed that the potential pressure that cats may exert on their prey is the biggest around dawn and dusk and in summer. During a daytime it is confined to the immediate vicinity of build-up areas.
The hypothesis tested concerned whether the diet of the tawny owl Strix aluco, as an opportunistic predator, does reflect increases in the density of bat populations in the owl’s hunting areas. In our study area, there was a mass use of toxic pesticides during which numbers of bats declined drastically, after which recoveries in the populations of most European species occurred. Thus, in Poland, numbers of bats reached their lowest levels in the 1980s. We examined the diets of tawny owls in Warsaw and the adjacent Kampinos Forest of central Poland, based on the remains of 9142 prey items. Bat specimens were found to comprise the following percentages of all vertebrate prey items: 1976–1989: 0.03–0.14%, 1990–1999: 0.32–0.40%, and 2000–2007: 0.54–1.71%. If the share taken by bats among mammalian prey is in turn considered, the analogous figures are 0.09–0.17%, 0.45–0.99% and 0.92–3.26%. Patterns in owl diets were consistent with trends in bat numbers at 15 large winter roosts located some 10–50 km from the study area in 1989–2006.