An attempt to determine the size of the Common Barn-owl’s (Tyto alba) hunting area based on its prey composition

The relative abundance of small mammal species detected from Common Barn-owl pellets reflects the landscape structure and habitat pattern of the owl’s hunting area, but it is also affected by the size of the collected pellet sample and the size of the supposed hunting area. The questions arise: how many pellets should be collected and analyzed as well as how large hunting area should be taken into consideration in order to reach the best correspondence between the owl’s prey composition and the distribution of habitats preferred by small mammals preyed in supposed hunting areas? For this study, we collected 1045 Common Barn-owl pellets in a village in southern Hungary. All detected small mammal species were classified into functional groups (guilds) preferring urban, open, forest and wetland habitats. The proportion of functional groups was compared to the proportion of these habitats around the pellet collection site within circles of one, two, and three km radius. Saturation curves showed that at least 300 pellets or ca. 600 mammalian remains are required for the detection of the 19 small mammal species. The share of small mammals detected in the prey and their functional groups according to their habitat preference showed an increasing consistency with the distribution of real habitats in the potential hunting area of a radius of 3 km around the owl’s breeding or resting place.

Diet of sympatric Barn Owls Tyto alba and Short-eared Owls Asio flammeus in an agricultural landscape in south-east Spain

The diets of the Barn Owl Tyto alba and the Short-eared Owl Asio flammeus have been extensively studied worldwide over the past few years, especially on the Iberian Peninsula. Nevertheless, very few studies have examined the diets and the trophic niche overlap in areas where these two raptor species occur in sympatry. As such, in this study we compared the diets of the Barn Owl and the Short-eared Owl inhabiting agricultural landscapes of the Vega de Granada, south-east Spain, based on pellet analysis. The diets were very similar, as both owls preyed mainly on small mammals, the Algerian Mouse Mus spretus being the prey most commonly found in pellets from both species. Although the diet of the Barn Owl was more diverse than that of the Short-eared Owl, the food niche overlap was very high, thus indicating a low interspecific trophic segregation. Despite the similarities between both diets, the frequency of the Mediterranean Pine Vole Microtus duodecimcostatus was much higher in pellets from the Barn Owl, thus suggesting that the Barn Owl may exert pest control in years when the Mediterranean Pine Vole occurs in high numbers.

When the barn-owl feasted on bats, an approach to taphonomic analysis

Small vertebrates are a key proxy for paleoenvironmental and paleoclimatic reconstruction, but a previous taphonomic analysis of the paleontological assemblage is needed before facing this kind of approach. Works concerning taphonomy of preyed small vertebrates are abundant in the literature, but chiropters are not usually included as they are only rarely predated. Here we analysed the content of two barn-owl (Tyto alba) pellets that exclusively contained bat remains. Our aim is to assess the effects of digestion inflicted by this predator on certain bat skeletal elements, specifically mandibles and lower teeth. All bat remains were assigned to Pipistrellus sp. They mostly presented slight alteration of the mandible and non-altered enamel, which is an expected result based on previous literature concerning this type of predator. Nevertheless, a few specific specimens showed much more intense alteration. This is most probably due to predator-related factors, although a higher degree of age-related tooth-wear in a specific bat cannot be dismissed.

Multi-Taxa Neo-Taphonomic Analysis of Bone Remains from Barn Owl Pellets and Cross-Validation of Observations: A Case Study from Dominica (Lesser Antilles)

Paleo- and neo-taphonomic analyses of bone assemblages rarely consider all the occurring taxa in a single study and works concerning birds of prey as accumulators of microvertebrate bone remains mostly focus on small mammals such as rodents and soricomorphs. However, raptors often hunt and consume a large range of taxa, including vertebrates such as small mammals, fishes, amphibians, squamates and birds. Bone remains of all these taxonomic groups are numerous in many paleontological and archaeological records, especially in cave deposits. To better characterize the predators at the origin of fossil and sub-fossil microvertebrate accumulations and the taphonomic history of the deposit, it is thus mandatory to conduct global and multi-taxa taphonomic approaches. The aim of this study is to provide an example of such a global approach through the investigation of a modern bone assemblage from a sample of pellets produced by the Lesser Antillean Barn Owl (Tyto insularis) in the island of Dominica. We propose a new methodology that allows us to compare different taxa (rodents, bats, squamates and birds) and to experiment with a cross-validation process using two observers for each taxonomic group to test the reliability of the taphonomic observations.

Environmental values of California winegrape growers and the use of barn owl nest boxes as a tool for integrated pest management

Synthetic pesticides from agriculture pose threats to biodiversity, and the adoption of alternative pest management is vital to meet rising crop demands while protecting native species. For example, the use of nest boxes for barn owls (Tyto furcata and T. alba) may help control rodent pests and reduce the use of rodenticides. However, the environmental perceptions of farmers and how receptive they are to alternative pest management practices remains uncertain. Traditionally, agricultural policies and programs have focused largely on the economic self-interest of farmers, but these narrow approaches have proven insufficient to describe and predict conservation behaviors, and the study of environmental value orientations (EVOs) may better explain farmers’ adoption of novel wildlife-friendly practices. The study of EVOs can help identify people as “mutualists”, meaning those who value the environment for its own sake, and “utilitarians,” meaning those who value the environment for the services it can provide. We surveyed 71 California winegrape growers in order to better understand how their underlying environmental values relate to the use of barn owl boxes and other sustainable practices. Overall, most winegrape growers had mutualist value orientations (64%). However, there was a disconnect between the use of barn owl boxes and EVOs, with most respondents (80%) reporting the use of owl boxes regardless of underlying values. This opens the door for future research to examine whether this is true of other wildlife-friendly farming practices.

Small mammals from barn owl Tyto alba pellets in a Mediterranean agroforestry landscape of central Italy

In order to investigate diversity patterns and similarities in the small mammal communities of an agroforestry landscape in western central Italy (Maremma of Lazio), we analyzed, in a multivariate setting (Cluster analysis, DCA-Detrended Correspondence Analysis), the prey content of barn owl Tyto alba pellets collected along one year in five sampling sites. Small mammal communities were composed by guilds typical of habitats included in agroforestry landscapes (croplands and mosaics, forests and ecotones, wet habitats and synanthropic ones). Since landscape matrices were characterized almost everywhere by croplands, typical agro-ecosystem species (Apodemus cfr. sylvaticus, Microtus savii, Mus domesticus and Soricidae) dominated in the majority of the collecting sites. The statistical analyses show how small changes in land use and cover can explain the faunal differences between sites, with the occasional presence of Arvicola italicus in wet habitats, and of Muscardinus avellanarius and Sorex samniticus in sites dominated by forest or agroforestry ecotones. Communities recorded in sites characterized by wet and forest habitats showed a higher distance from the others, dominated by croplands. Communities occurring in landscapes with the lowest habitat diversity showed also the lowest species diversity.