Ludwik Tomiałojć
Ornis Polonica 2011, 52: 1–25
https://doi.org/10.12657/ornis.2011.1.0
Abstract: Bird censuses were carried out in two parks of Wrocław, a down-town one (Słowacki Park, 7–7.5 ha) and in a 17 ha section of the larger Szczytnicki Park, once a riparian forest. In the first one, counts were performed each year in 1970–1999 and 2008–2010, while in the second one during 1970–1974, 1986–1988, 2000–2002 and 2009–2010. Territory mapping method (8–10 to 10–12 visits/season) was applied by the same observer, recently using a hearing apparatus and visiting plots more often. The parks differ by: (a) Słowacki Park – tree stand with few bushes planted before 1900, intensive human presence, with Hooded Crows Corvus cornix present since 1972, (b) Szczytnicki Park – high luxuriant tree stand with few bushes on alluvial soils, moderate numbers of visitors and predators arrived mostly in the late 1970s (two marten species, sporadic raptors and Hooded Crows). In both areas usually a few to a dozen of artificial nest boxes were present. Due to war devastations, both parks were in a “wild” state till the 1960s. After restored predation an overall density of breeding birds dropped in Słowacki Park from c. 294 to 173 p/10 ha, with significant declines of previously abundant species (Wood Pigeon Columba palumbus, Collared Dove Streptopelia decaocto, Rook Corvus frugilegus, Jackdaw C. monedula, Blackbird Turdus merula, Tree Sparrow Passer montanus). Reduction of prey species was diversified in time: vulnerable (Wood Pigeon) declined soon after arrival of crows, other ones after their replenishment. In Szczytnicki Park, with a more stable tree stand, avifauna has changed considerably: over a dozen of species have disappeared, some are close to local extinction, while 6–8 new ones have settled. After arrival of predators some common species ceased to breed (Tree Sparrow, Jackdaw) or their abundance declined by 2–3 times (turdids, columbids). Overall density has dropped from 230 to 145–149 p/10 ha. Main declines in this bird assemblage occurred during the 1980s (arrival of Pine Martens Martes martes) and in 2008–2010 (replenished Hooded Crows). Records of predator attacks on bird nests/broods confirmed this pressure. Antipredator behaviour in some prey species persisted for years after Pine Marten disappearance.
