The Role of Predators in Shaping Urban Bird Populations: 2. Is Predation Pressure Increased or Decreased in Urban Landscapes?

Contrasting points of view on the degree and results of predation pressure in cities compared to natural/rural landscapes are considered. One of these points of view states that it is decreased due to the absence of some key native predator species and the impoverishment in species composition of predator assemblages, and the other states that it is increased due to the high abundance of synanthropic and domestic predators. The absence of some forms of intense human persecution in modern cities, such as hunting, also fits well with the first view, although this cannot be considered a main attractive factor for all urban species, since most of them are not persecuted outside cities as well. It has been shown that the data in the world literature on reproductive losses caused by predation (these are mainly data on nest predation) are very contradictory, and there are many studies in favor of each of the hypotheses. Different groups of prey, such as hole- and open-nesting species, are vulnerable to varying degrees to one or another nest predator, so losses can be reduced for some species and increased for others in the same city. In one species at different periods of time or in different prey species, processes corresponding to both points of view can occur at the same time. It is not yet possible to judge the correctness of opinions concerning predation pressure on adults due to an acute lack of data. The indirect trait-mediated effects of the presence of predators in urban versus non-urban environments also awaits study.