Costs and benefits of breeding in human‐altered landscapes for the Eagle Owl Bubo bubo

Abstract

We studied a population of 23–25 Eagle Owl Bubo bubo pairs between 1994 and 2000 in a 1330‐km2 study plot in the central‐eastern Italian Alps. Compared to random sites, territories were located at lower elevation and closer to intensively cultivated‐urbanized valley floors. Early laying was associated with low elevation and negatively affected productivity. Diet was dominated by rats, hedgehogs and dormice (n = 978 prey items), all of them typical of low‐elevation habitats. Higher productivity was associated with a higher proportion of rats in the diet of individual pairs. Low availability of rats resulted in a more diverse diet, in turn associated with low productivity. Territories were occupied every year in a non‐random fashion, and those most occupied were characterized by higher productivity and higher occurrence of the favoured prey types in the diet, suggesting they were of superior quality. Eagle Owls also paid a cost associated with nesting near human‐altered habitats: the main cause of mortality reported to local authorities was electrocution. This is an increasing cause of death for many European populations and may be a cause for conservation concern. Human persecution is also an important cause of mortality in some parts of the European range. Apart from such costs, the study population appeared to have adapted well to the proximity of humans: estimates of density and productivity were comparable to those recorded elsewhere in Europe. The pattern found in our population also held at higher spatial scales: data from 17 European populations showed density to be highest in low‐elevation, human‐altered landscapes.

The importance of micro-habitat in the breeding of Barn OwlsTyto alba

“…At lower altitudes the Barn Owls probably bred earlier than at higher altitudes, because spring starts earlier and rodents therefore reproduce earlier. Breeding earlier at lower altitudes has also been found in other bird species (Sanz 1998, Marchesi et al 2002, Lu et al 2010, Tieleman 2010.…”

Intra- and interhabitat differences in hedgehog distribution and potential prey availability

“…The eagle owl [ Bubo bubo (Linnaeus) ] is a signifi cant predator of hedgehogs in areas of Europe where the two species coexist (Marchesi et al 2002, Penteriani et al 2002. In France, hedgehogs were amongst the most common mammalian prey consumed by eagle owls (Penteriani et al 2002 ) and hedgehogs also dominated their prey in Italy (Marchesi et al 2002 ). (Riber 2006 ), as well as areas where they are not, e.g., UK (Reeve 1981, Doncaster et al 2001, Shanahan et al 2007, Hof 2009 ).…”

“…Although an increased risk of predation at hedgerows may explain the foraging activity of the hedgehogs in the current study, there are only a small number of potential avian predators in Ireland. The eagle owl [ Bubo bubo (Linnaeus) ] is a signifi cant predator of hedgehogs in areas of Europe where the two species coexist (Marchesi et al 2002, Penteriani et al 2002. In France, hedgehogs were amongst the most common mammalian prey consumed by eagle owls (Penteriani et al 2002 ) and hedgehogs also dominated their prey in Italy (Marchesi et al 2002 ).…”

Impact of Dominant Predators on Territory Occupancy and Reproduction of Subdominant Ones within a Guild of Birds of Prey

“…Based on the available prey lists, intraguild predation is a widespread phenomenon among various birds of prey, particularly among some of the largest ones [3,7]. However, birds of prey seemed to be occasional and uncommon prey for other birds of prey compared with their principal prey [8][9][10][11]. This general scarcity of intraguild predation suggests that the rate at which birds of prey are taken by other birds of prey is roughly proportionate to their availability.…”

“…In Europe, the eagle owl Bubo bubo (Linnaeus 1758), the largest species of owls, preys on various kinds of mammalian and avian prey, while the northern goshawk Accipiter gentilis (Linnaeus 1758) is the principal diurnal predator of medium-sized birds; both species are among the most effective predators on other birds of prey [3,7,9,11,19,20]. Both of these species have been shown to have depressing effects on populations of some smaller-sized species of birds of prey [5,6,10,21,22].…”