Non-native spruce plantations represent a suitable habitat for Tengmalm’s Owl (Aegolius funereus) in the Czech Republic, Central Europe

Abstract

Anthropogenic activity can lead to deforestation and subsequent dramatic impacts on forest-dwelling animal species. In this study, we investigated the habitat use of a forest raptor (Tengmalm's Owl Aegolius funereus) in an air-polluted area of the Ore Mountains (Czech Republic) that has been restored by non-native spruce. Based on a 14-year Tengmalm's Owl nest-box breeding dataset, we found that the percentage of native Norway Spruce forest was higher for occupied nest boxes than for unoccupied ones within close surroundings of the nest (buffer radius of 25 m). Meanwhile, the percentage of nonnative Blue Spruce (originally from Northern America) was higher for occupied nest boxes than for unoccupied ones within the home-range breeding area (buffer radius of 750 m). Moreover, the surroundings of non-predated nests (radius of 750 m) showed a higher percentage of Blue Spruce and a lower percentage of deciduous trees than surroundings of nests predated by Pine Martens. Although small mammal availability was not affected by habitat categories, we found a positive correlation between the percentage of Apodemus mice in the diet of owls and the percentages of both Blue Spruce and open forest area within the foraging area radius (750 m). We suggest that adult owls and young fledglings use remnants of tall, oldgrowth Norway Spruce forests as a safe refuge against avian predators, while secondary stands of non-native Blue Spruce are suitable for hunting both main prey types (Apodemus mice and Microtus voles), and also ensure good protection against nest predation by Pine Martens.

Indirect food web interactions affect predation of Tengmalm's Owls Aegolius funereus nests by Pine Martens Martes martes according to the alternative prey hypothesis

“…) and with the proportion of hunting habitat suitable to catch mice (Zárybnická et al . ); however, we found no such relationships for the abundance of Microtus or Myodes voles. These findings support the predictions of the alternative prey hypothesis between a mammal predator and a cavity bird nester, two predators that compete for the same small mammal resource in temperate areas.…”

Apodemus mice as the main prey that determines reproductive output of tawny owl (Strix aluco) in Central Europe

“…In agreement, Eurasian Kestrels in Central Europe during vole scarcity feed mainly on insects and Apodemus mice are not frequent prey (Riegert and Fuchs 2004). (2) Habitat preferences of Apodemus mice for wooded and ruderal habitats (Anděra and Horáček 2005) are consistent with the hunting habitat preferences of tawny owl (Kajtoch et al 2015), long-eared owl (Lövy and Riegert 2013) and boreal owl (Zárybnická et al 2015b). Representations of other components of tawny owl diet considerably vary across the European continent, but in general, proportions of birds (12.1%), insectivores (1.2%) and amphibians (2.2%) in the diet of our tawny owls are comparable with other studies (e.g., Kirk 1992;Kekkonen et al 2008;Grzedzicka et al 2013).…”

Home range size of Tengmalm’s owl during breeding in Central Europe is determined by prey abundance

“…This area was severely damaged by air-pollution in the 1970s, with most coniferous trees above the altitude of 500 m a. s. l. dying out as a result; the study area (110 km 2 , 730–960 m a. s. l.) has been artificially replanted, with the predominant species being blue spruce ( Picea pungens , occupying approximately 28% of the study area), Norway spruce ( Picea abies , 26%), birch ( Betula sp., 11%), European mountain ash ( Sorbus aucuparia , 5%), European beech ( Fagus sylvatica , 4%) and European larch ( Larix decidua , 4%). Outside the forested parts the vegetation is dominated by wood reeds ( Calamagrostis villosa ) and solitary European beech [ 61 ]. To compensate for the lack of natural tree cavities, 233 wooden nestboxes lined with wood chips (with the base 25x25 cm, height 40 cm and with an entrance hole 8 cm in diameter) have been installed gradually in the area since 1999, and virtually the whole local population of Tengmalm’s owl breeds in these nestboxes.…”