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Abstract
Mammalian prey of barn owls Tyto alba in various district electoral divisions in County Cork was examined against areas under cereals, sugar-beet, potatoes, other crops, hay, pasture, silage, rough grazing, woodland and the residual area - including farms of less than 5ha, commercial conifer stands and unimproved land - in those divisions. House mice Mus domesticus, the most variable constituent in the prey (<1% to 75%) and occurring mainly around farmsteads, were strongly associated with other crops, the largest component of which is fodder beet. The latter is correlated with cereal-based fodder concentrates stored on farms, which, we argue, largely determine the population of house mice. Other consistent positive associations were between field mice Apodemus sylvaticus and residual area; pygmy shrew Sorex minutus and woodland; and common rat Rattus norvegicus and potatoes. Using polychotomous stepwise logistic regression, mathematical models were constructed with land categories as independent variables and numbers of the different prey species as dependent variables. Such models can predict prey from data on land use. The most important explanatory variable was other crops, particularly for house mice. Pasture, which provides minimal cover and food for small mammals, was not an explanatory variable. Refinements in the collection of data, to improve models, are suggested.
... Research findings have reported an increase in the darker coloured tawny owls in the 2000s, which is suggestive of an adaptation mechanism to global climate warming. Plumage pigmentation has been suggested to be an essential trait of organism's resilience to environmental stress [33,34]. However, female plumage colouration has not been linked with body size, hatching date, brood size or number of offspring produced [34]. ...
... Nine nocturnal species of raptors have been recorded in the La Selva El Ocote Biosphere Reserve [30]. Three of them (black-and-white owl, Ciccaba nigrolineata; ferruginous pygmy owl, Glaucidium brasilianum; and spectacled owl, Pulsatrix perspicillata) include birds in their diet [31][32][33]. Twenty-five diurnal raptors have also been recorded [30], of which the collared forest falcon and the barred forest falcon (M. ruficollis) feed mainly on birds [33,34]. ...
... Twenty-five diurnal raptors have also been recorded [30], of which the collared forest falcon and the barred forest falcon (M. ruficollis) feed mainly on birds [33,34]. The predators used as a model in this study were selected based on their dietary habits (mainly birds) and hunting behaviour in the interior of the forest [34]. ...
This book has a review on the relationships between bats and owls in Europe and it describes the biological control of rats by owls in Malaysia. It also presents the prey-predator interactions in a tropical forest in Mexico, and provides an overview on owl taxonomy and the breeding biology of owls. From numerous owl belief and myth studies, described in this book are those of the lesser known Central Asian countries where owls are often worshipped for their supernatural powers.
... Furthermore, changes in diet as seen in pellets reflect real changes in availability of small mammals species (Clark and Bunck 1991). In spite of some limitations, this method has been successfully used to study patterns of small mammal distribution at a geographical scale, through gradients of elevation or latitude (Alegre et al. 1989;Clark and Bunck 1991;Torre et al. 1996;, as well as at the landscape and habitat scales (Cooke et al. 1996;Torre et al. 1997). The study of scats of carnivores with generalist and opportunistic feeding habits, such as the common or small-spotted genet Genetta genetta , one of the commonest carnivores in NE Spain , has not been previously used to study small mammal distribution, however. ...
... Más aún, los cambios en la dieta reflejados en las egagrópilas reflejan cambios reales en la disponibilidad de micromamíferos (Clark y Bunck 1991). A pesar de algunas limitaciones, este método ha sido usado con éxito para estudiar los patrones de distribución de los micromamíferos a escala geográfica, a lo largo de gradientes de latitud y altitud (Alegre et al. 1989;Clark y Bunck 1991;Moreno y Barbosa 1992;Torre et al. 1996;, y también a escalas del hábitat y del paisaje (Cooke et al. 1996;Torre et al. 1997). Sin embargo, el estudio de los excrementos de carnívoros con hábitos alimentarios generalistas y/o oportunistas, como la gineta Genetta genetta (Rosalino y Santos-Reis 2002;, uno de los carnívoros más abundantes en los bosques del nordeste ibérico , no ha sido previamente utilizado para estudiar la distribución de los micromamíferos. ...
... Furthermore, changes in diet as seen in pellets reflect real changes in availability of small mammals species (Clark and Bunck 1991). In spite of some limitations Spitz 1966, Clark andBunck 1991), this method has been successfully used to study patterns of small mammal distribution at a geographical scale, through gradients of elevation or latitude (Alegre et al. 1989, Clark and Bunck 1991, Torre et al. 1996, and at the landscape or land-use scales (Cooke et al. 1996, Torre et al. 1997. ...
... Previous studies of dietary response of T. alba generally were based on pellet contents without assessing availability of prey (e.g., Goutner and Alivizatos 2003;Pardinas and Teta 2005;Leonardi and Dell'Arte 2006;Charter et al. 2009;Platt et al. 2009). It was sometimes assumed that pellet analysis provided a reliable indication of the proportion of vertebrates in the field (Taylor 1994;Cooke et al. 1996). This implies that prey diversity in the diet of T. alba directly reflects the community structure and composition of small mammals, and so T. alba capture prey randomly (Ba et al. 2000). ...
... This study was carried out as part of the '' Rodents and Rural Planning'' 1992-1996 contract and the ''Plan d'action campagnol 2001-2007, with financial support of the Conseil régional de Franche-Comté (France). We are extremely grateful to Kent Livezey for his kind guidance and support in the revision of the earlier version of the manuscript. ...
... Moreover, simultaneous trapping on numerous sites is time-consuming and often unrealistic when we aim to assess the structure and the composition of small mammal community within a large diversity of landscape context (Millan de la Pena et al., 2003). This is why other indirect approaches, such as Barn Owl pellet analysis have been extensively used (Hanney, 1962, Glue, 1971, Perrin, 1982, Clark and Bunck, 1991, Millan de la Pena et al., 2003 owing to the generalist feeding behaviour of this raptor (Cooke et al, 1996). As for trapping techniques, biases associated to this second techniques have been reported (Glue, 1971). ...
... It is known to focus almost exclusively on small mammals, and pellets are easily found and analyzed (Bunn et al., 1982, Taylor, 1994. For all these reasons, this is one of the most widely used method to study richness and composition of small mammal communities across ecological gradients (Giraudoux et al.1990, Clark and Bunck, 1991, Cooke et al., 1996. ...
During the last decades, drastic changes in farming landscape structure and composition have been
induced by changes in agricultural production methods and policies (increase of machinery use, expansion of cultivated areas to the detriment of semi-natural habitats, growing use of chemical products....). A question increasingly associated with all these changes in modern agriculture is to known if there have been impacts of agricultural intensification on biodiversity.
In that way, we study a community of small mammals (rodents & insectivores < 40g) living in hedgerows, in three contrasted farming landscapes differing by their level of land-use intensity and hedgerow network density, giving an agricultural intensification gradient. The framework of the study is : (1) to characterize the composition and the structure of the community in the agricultural landscapes, (2) to identify (in a multi-scale approach) which environmental variables could be
predominant for explaining differences in species assemblages between hedgerows, (3) to characterize seasonal variations of the community and component populations in response to landscape dynamics. (4) We also compare abundances of two small mammal predators, Buteo buteo and Falco tinnunculus, in response to the composition of the three sites, and to small mammal availability.
The results show the importance to develop an approach utilizing several organization levels and observation scales. Diversity, abundance, composition and biomass of the community, as well as abundance of the two raptor species, clearly differ between the study sites, showing an influence of agricultural intensification on the small mammal community and an higher trophic level. Both
landscape and habitat scale are implied in structuring species assemblages. Seasonal patterns in the small mammal populations are the same whatever the site, but amplitude fluctuations are different, particularly for the dominant species.
These results could permit to propose action plans for the conservation of biodiversity in agricultural landscapes.
... En general, dichos trabajos justifican el método teniendo en cuenta que las egagrópilas producidas por las lechuzas reflejan fielmente su dieta y que los cambios en la dieta demuestran cambios en la disponibilidad de las especies en la comunidad de micromamíferos (Clark y Bunck 1991, Taylor 1994) debido al carácter oportunista del predador (Díaz et al. 1996). Aparte de algunas limitaciones (SaintGirons y Spitz 1966, Clark y Bunck 1991), éste es un método útil para establecer patrones de distribución y abundancia de micromamíferos a escala geográfica (ej: variaciones en relación a la altitud o latitud, Clark y Bunck 1991, Pérez-Barbería 1991, Moreno y Barbosa 1992, Torre et al. 1996 ) e incluso paisajística (ej: variaciones entre tipos de cultivos, Cooke et al. 1996, Torre et al. 1997 ). Sin embargo, la interpretación de los patrones de riqueza a dichas escalas puede ser dificultosa si no se tiene en cuenta el esfuerzo muestral realizado (Rahbek 1995 ). ...
... Así pues, en el estudio de Moreno y Barbosa (1992), el patrón latitudinal de la riqueza queda reforzado al incorporar esta variable en el análisis, ya que las muestras de las zonas bajas detectan más especies debido a su mayor tamaño medio. La aparición de interacciones confirma que las relaciones entre la riqueza y el tamaño de muestra pueden ser distintas entre los niveles de un factor analizado (altitud: Gil et al. 1986, Culí et al. 1989 tipos de cultivo, Torre et al. 1997; análisis latitudinal conjunto de la riqueza), hecho que llevaría a respaldar la imposibilidad de aplicar determinados índices de riqueza en la mayoría de los casos (Ludwig y Reynolds 1988). El análisis de los residuos confirma el efecto negativo del incremento excesivo del esfuerzo de muestreo sobre la riqueza en áreas con comunidades pobres, aunque este esfuerzo deba ser superior en áreas con comunidades ricas. ...
... Population level responses to non-native small mammals have already been recorded with Barn Owls in Ireland, with their numbers increasing in apparent response to the presence of Greater White-toothed Shrew, and previous to this, the Bank Vole (Lusby et al. 2022, McCarthy et al. 2023. It is now evident that Field Voles, Greater White-toothed Shrews and Bank Voles can account for a substantial proportion of Barn Owl diet in Ireland and are often the most dominant prey in the diet (Smal 1987, Cooke et al. 1996, Smiddy 2018. Aside from influencing Barn Owl diet and potential breeding ecology impacts, the presence of Field Voles in Ireland may also lead to other effects on Barn Owls, and may influence the risk of exposure to rodenticides if there is a significant change in the diet. ...
The Field Vole is a small mammal species new to the island of Ireland which, in its native range, is often an important component of raptor diet, including that of the Barn Owl. The Barn Owl is a Red-listed Bird of Conservation Concern in Ireland, having experienced widespread declines since the 1960s, in part as a result of reduction of food availability. This study sought to determine whether the newly discovered Field Voles were featuring in Barn Owl diet where the ranges of both species overlap on the island of Ireland. We collected 39 Barn Owl pellets and pellet debris from the two closest known Barn Owl nest sites to the original point of discovery of the Field Vole. Results from the pellet analysis show that Field Voles are featuring prominently in Barn Owl diet at these two nest sites, accounting for 34.1% and 45.3% of prey items in each site, respectively. At both sites, Field Vole was the second most commonly recorded prey item after that of Wood Mouse. These results give an insight into the potential impact that Field Voles may have on Barn Owl diet and ecology in Ireland as their range continues to expand.
... However, we cannot rule out that the sampling method used to be spatially biased due to species detectability and habitat issues, owing to the fact that the diet of barn owls overrepresents the open-land species and underrepresents the forest species [29,45]. Despite limitations, the diet of barn owls has had a widespread application for detecting changes in the small mammal communities in European agricultural ecosystems [28,37,[46][47][48][49][50][51]. Furthermore, this method has also been applied to depict the patterns of spatial distribution along strong environmental gradients caused by geographic and climatic factors [18,19,32,35]. ...
We analyzed the two main drivers (climate and land uses) shaping the composition of small mammal communities at 16 localities situated in the confluence of the Mediterranean and Eurosiberian regions (Barcelona, Spain). The study area represents a land use and land cover gradient showing urbanization and crop intensification in the lowlands and forest encroachment in mountain areas. We identified 2458 small mammal individuals of 12 different species from barn owl (Tyto alba) pellets. Three open-land species (Microtus duodecimcostatus, Crocidura russula, and Mus spretus) and one forest/generalist species (Apodemus sylvaticus) were dominant in the diet, accounting for 93% of prey. In order to disentangle the effects of both main drivers on the small mammal community, we used partial constrained ordination techniques, which allowed us to determine the pure effects (and shared effects) of the environmental factors. Land use predictors explained 33.4% of the variance (mostly crops), followed by 23.4% of the variance explained by the geo-climatic variables (mostly rainfall), and an additional 24.8% of the variance was shared by both groups of pre-dictors, totaling 81.6% of environmental variance. The remaining 18.4% of variance was unexplained by environmental matrices. This pattern was consistent with expected associations of species and biotic influences at small spatial scales and highlighted that the number of species increased from the crops in the lowlands towards the highlands covered by deciduous and coniferous forests.
... Raptors and other top predators are often used as proxies to assess biodiversity (Steneck et al. 2002;Sergio et al. 2005Sergio et al. , 2008Sergio et al. , 2009Dunk et al. 2006), and increases in raptors following conservation actions may indicate that efforts have been successful (Burgas et al. 2014, Ripple et al. 2014, Senzaki et al. 2015. Gray hawks (Buteo plagiatus) are a good model species with which to investigate the effect of conservation measures because they are a top predator that has a generalist diet; thus, their diet likely reflects the relative abundance of prey species in breeding territories (Cooke et al. 1996, Torre et al. 2015. Change in the spatial distribution and diet of gray hawks may therefore provide evidence of changes in prey populations. ...
Desert riparian ecosystems are among the most threatened biodiversity hotspots in the United States, and efforts to conserve them have been increasing. In 2010–2011 and 2014–2016, we examined shifts in the distribution, habitat characteristics, diet, nest success, and productivity of the gray hawk (Buteo plagiatus), 25 years after a Riparian National Conservation Area was established along the San Pedro River in Arizona, USA, to determine how the removal of grazing and agriculture may have affected the ecosystem. The gray hawk population increased and expanded from mesquite (Prosopis spp.)‐dominated areas that they historically occupied into areas that were dominated by grassland. In contrast with the 1990s, percent of mesquite cover in pairs' territories did not correlate with their productivity. Gray hawk diets also included more mammals in our study period, particularly in territories with more grassland. We propose that conservation measures created habitat for gray hawks in areas that were previously unsuitable by allowing grasslands to regenerate and become habitat for their prey, and that management strategies in the San Pedro Riparian National Conservation Area could serve as a model for conservation of other desert riparian ecosystems. © 2020 The Wildlife Society. Gray hawks increased in a riparian area following the removal of livestock grazing, and began to thrive in territories that consisted primarily of grassland and were previously used very little. We propose that eliminating grazing allowed grasslands to regenerate and support small‐mammal populations, providing quality foraging areas for gray hawks.
... Several studies suggested that the yearly and seasonal variations in the diet composition and thus the plasticity of the food-niche breadth of the Barn Owl reflected local resource conditions, especially the density fluctuation of small mammal preys and changes in the composition of the small mammal assemblages (Milana et al. 2016). The population and community attributes of this main prey groups of Barn Owls were determined by changes in the vegetation cover (Lovari et al. 1976, Marti 1988, Pezzo & Morimando 1995, Bontzorlos et al. 2005, land use and agricultural activity (crop rotation, frequency of mowing or harvesting) (Cooke et al. 1996, Askew et al. 2007). ...
This study investigated the dietary niche of the Barn Owl (Tyto alba) in an intensively farmed landscape, based on pellet samples from 12 nesting pairs containing 25 animal taxa and 1,994 prey items after the breeding season in 2016. Based on land use categories of the buffer area around each nest, three landscape types (agricultural, mosaic, urban) were considered, to analyse the diet composition and food-niche parameters. Niche breadth was calculated at the local and landscape level. Small mammals were the most frequent in the diet than other prey in each of the landscape types. The Common Vole (Microtus arvalis) , considered to be an important agricultural pest was the most numerous prey in all landscape groups. The trophic niche of Barn Owl varied between 0.69 – 0.86 at the local level, and the overall value of niche breadth was significantly higher in the urban than in the other two landscape types. Our results showed that the increase of Common Vole frequency lead to a decrease in niche breadth; significantly negative relationship was detected between these parameters. Despite differences in niche breadth, similarly high niche overlaps were detected by the randomisation test in the three landscapes. Our results suggest that the diet composition of Barn Owls, mainly their food-niche pattern, reflected prey availability in the comparison of the studied landscapes, which pointed out that it is necessary to examine the dietary difference of Barn Owls at the finer scale of land use.
... This study presents the first account of barn owl diet within the combined ranges of both invasive species, and briefly compares the results with other published studies of barn owl diet from County Cork inside and outside the range of the bank vole. Numbers and biomass of rodents and shrews in barn owl diet from studies in County Cork were compared where, among invasive species, (a) no bank voles were present (n=1512), (b) bank voles were present (n=16,335), and (c) bank voles and greater whitetoothed shrews were present together (n=508) (Smal 1987;Cooke et al. 1996;Farnsworth et al. 2002;Kelleher et al. 2010;Doyle et al. 2015) (Fig. 1a and b). In the absence of the bank vole, brown rats, field mice and house mice provided roughly an equal percentage of prey (30-38% biomass) (Fig. 1b). ...
This study presents an account of the diet of barn owls Tyto alba (Scopoli) which fed mainly on two invasive species in County Cork, Ireland during a one-year period. Greater white-toothed shrew Crocidura russula (Hermann) (68%) and bank vole Myodes glareolus (Schreber) (18%) constituted 86% of diet by number and 76% by biomass. Among indigenous species, numbers of brown rats Rattus norvegicus (Berkenhout) (2.8%), field mice Apodemus sylvaticus (Linnaeus) (9.6%), house mice Mus domesticus (Linnaeus) (1.2%) and a single pygmy shrew Sorex minutus Linnaeus (0.2%) formed a combined total of only 13.8% among the total of 508 rodent and shrew prey items recovered and identified. Barn owls preyed almost exclusively on invasive species as soon as they became established in the environment, the greater white-toothed shrew being an important prey species in all seasons of the year.
... Upon long-term studies of their diet content spatial and temporal changes of the small mammal composition in their hunting area can be detected (Bunn et al. 1982, Tores et al. 2005. This method is also suitable for detecting the effect of land use changes on small mammal communities (Cooke et al. 1996, de la Peña et al. 2003, Rodríguez & Peris 2007. ...
The prey composition of the Barn Owl (Tyto alba) can be monitored indirectly by pellet analysis and we used this method to investigate less known small mammal species of Zala County. The number and abundance of small mammal species depend on the structure of the landscape of Barn Owls' hunting area, therefore we analysed landscape features in the surrounding circles with 2 km radius around the sampling sites. In 2016 we collected 1106 pellets from 13 sampling localities. From the pellets we identified 21 species of 3022 individuals of small mammals (more than 98% of prey). Among the 21 species there was the rare Parti-colured Bat (Vespertilio murinus) and a new species for the county the Steppe Mouse (Mus spicilegus). Positive correlation was found between the diversity of the small mammal fauna of each sampling site and the landscape complexity (number of the landscape patches) of the Barn Owl hunting area. Relative abundance of the Wood Mouse (Apodemus sylvaticus) showed positive correlation with the number of landscape patches, while the abundance of the Lesser White-toothed Shrew (Crocidura suaveolens), the Miller's Water Shrew (Neomys anomalus), the Striped Field Mouse (Apodemus agrarius) and the Harvest Mouse (Micromys minutus) was higher in hunting areas with more homogenous landscapes. Significant correlations were found between the relative abundance of some small mammal species and the landscape structure of the potential hunting area of owls that confirmed the consistency in habitat preference of some species. Our results proved that the prey-composition of Barn Owls reflects the land use through the distribution and abundance of small mammal species, therefore this method is suitable for ecological analyses of landscape.
... Analysis of its prey offers an important source of information on the composition and dynamics of prey species communities within the Barn Owl's foraging area (Alivizatos and Goutner, 1999;Poprach, 2008). The Barn Owl's diet may be affected by the prey available in a particular geographical region (Bontzorlos et al., 2005;Roulin and Christe, 2013) and densities of prey species (Bernard et al., 2010), but also by land use or agricultural interventions (Cooke et al., 1996;de la Peña et al., 2003;Askew et al., 2007;Teta et al., 2012). Agricultural intensification is associated with a loss of natural habitat, loss of crop diversity and increased chemical inputs (Foley et al., 2005). ...
VESELOVSKÝ TOMÁŠ, BACSA KRISTIÁN, TULIS FILIP. 2017. Barn Owl (Tyto Alba) Diet Composition on Intensively Used Agricultural Land in the Danube Lowland. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 65(1): 0225–0233. Based on pellets analysis from five localities in south western Slovakia (Malá Mužla, Malé Ripňany, Obid, Opatovský Sokolec and Tešedíkovo), we studied the diet composition of Barn Owl (Tyto alba) in intensively cultivated agricultural lands. A total of 6218 specimens of prey, 17 mammalian and 7 bird species were identified. The main prey species found in all food samples was the Common Vole (Microtus arvalis), varying between 56 % and 67 %. The proportion of synanthropic species (Rattus norvegicus, Passer domesticus) and species inhabiting agricultural landscapes (Crocidura leucodon, Crocidura suaveolens, Mus sp.) increases in localities with a lower ratio of the Common Vole. The results suggest land use affects the diet of Barn Owls, confirming conclusions which have been drawn in previous studies. From faunistic point of view, discovering the Pannonian Root Vole (Microtus oeconomus mehelyi) in the diet from Malá Mužla was important.
... Con esta metodología se obtienen índices de abundancia y no densidades reales de la especie, datos que solamente se podrían obtener mediante trampeo. No obstante, numerosos autores consideran que el estudio de la dieta de la lechuza común refleja con bastante precisión la composición de las poblaciones de micromamíferos de la zona de estudio (Ticehurst 1935, Taylor 1994, Cooke et al. 1996. Por su parte, Ba et al. (2000) afirman que la diversidad de presas en la dieta de la lechuza común refleja directamente la estructura de la comunidad y la composición de micromamíferos, ya que la lechuza captura sus presas al azar y sin ninguna selección o preferencia. ...
The Junta de Castilla y León carried out several campaigns of control of common vole (Microtus arvalis) from 2007 to 2009, which coincided with a demographic explosion of the species. Anticoagulants products like chlorophacinone and bromadiolone were used during these campaigns. Information on the treatment campaigns which used rodenticides was compared with two studies which had been carried out to estimate the abundance of common vole, so as to evaluate the effectiveness of such treatments on the control of Microtus arvalis populations. The first study is based on the percentage of Microtus arvalis in barn-owl (Tyto alba) diet and the second by making road transects to find the abundance of diurnal birds of prey. Sixteen batches of barn-owl pellets were analysed –one each trimester, between January 2006 and december 2009– and 3,964 items of prey were identified. 96.3% of them were micromammals of seven species, and 63.7% were common vole. The percentages of Microtus arvalis / trimester varied from 18.0% –after the collapse of a demographic explosion– to 96.4% at the demographic explosion’s peak. These results made it possible to detect two demographic explosions, one starting at the beginning of the second trimester of 2006 and finishing in the second trimester of 2008. The second started at the second semester of 2009 and it seemed to enter a collapse stage at the end of the same year. On the road, 5,387 birds of prey of fifteen different species were counted from January 2005 to December 2009. This is a monthly Kilometric Abundance Index average of 69.0 individuals/100 km. The data showed that peaks of abundance of birds of prey coincided in time with both common vole demographic explosions. Nevertheless, the period considered for each demographic explosion was significantly shortened. According to the bird data, the first cycle started in July 2006 and continued until February 2007. The second cycle started in May 2009 and continued until December 2009. Both studies reveal the ineffectiveness of the chemical treatments, which were carried out some months after the beginning of the demographic explosion, which was already at its highest peak or at collapse stage. The effect of these treatments on non-target species is also discussed.
... Barn owl pellet analysis, a non-invasive sampling method, was able to detect significant shifts in the small mammal community composition and structure. The method has been proved efficient for detecting changes in the small mammal frequencies of occurrence in agricultural environments related to different farming practices (Cooke et al. 1996;Torre et al. 1997;Milla´n de la Pen˜a et al. 2003;Rodriguez and Peris 2007), and is considered as a valuable method for assessing small mammal populations and their change over time (Love et al. 2000;Meek et al. 2012). Accuracy of the method is based on the well-established fact that barn owls are generalist predators of small animals whose diet closely track spatial and temporal changes in relative prey abundance (Tores et al. 2005;Bernard et al. 2010). ...
... It is also highly unlikely that there has been a long-term presence of the greater white-toothed shrew in Ireland without it being recorded either as fossil material or as a recent member of the Irish mammal fauna. Previous extensive analyses found no evidence of white-toothed shrews in barn owl and raptor pellets in Ireland (Fairley & Clark, 1972;Fairley, 1973;Clark, 1974;Smal, 1987;Fairley & Smal, 1989;Cooke et al., 1996;Foley et al., 2006;O'Connell et al., 2006). More recent surveys from 1997 to 2001 of the bank vole, another introduction to Ireland (Claassens & O'Gorman, 1965) also failed to record the presence of the greater white-toothed shrew, despite good coverage of Tipperary and Limerick (Meehan, 2005). ...
... Barn owl pellet analysis, a non-invasive sampling method, was able to detect significant shifts in the small mammal community composition and structure. The method has been proved efficient for detecting changes in the small mammal frequencies of occurrence in agricultural environments related to different farming practices (Cooke et al. 1996;Torre et al. 1997;Milla´n de la Pen˜a et al. 2003;Rodriguez and Peris 2007), and is considered as a valuable method for assessing small mammal populations and their change over time (Love et al. 2000;Meek et al. 2012). Accuracy of the method is based on the well-established fact that barn owls are generalist predators of small animals whose diet closely track spatial and temporal changes in relative prey abundance (Tores et al. 2005;Bernard et al. 2010). ...
Human-induced landscape changes are expected
to have strong effects on the composition and
structure of terrestrial small mammal communities
(Orders Rodentia and Soricomorpha). However, testing
such expectations is difficult due to low detectability of
these animals. We used analyses of barn owl (Tyto alba)
pellets sampled in the same roosting places during
1977–1991 and again in 2011–2014 to (a) document
small mammal community changes and (b) relate them
to changes in land use. Forest and synanthropic small
mammals increased by a 7 % between both periods,
whereas open-land species decreased by 13 %. Manmade
loss (crops and meadows) and expansion (forest
and urban) of relevant habitat types were closely related
to these changes. Localities with land use changes opposite
to the general trend showed also an opposite
trend in small mammal community change. Land use
heterogeneity increased and dominance decreased between
both sampling periods, and this pattern was paralleled
by an increasing trend in diversity and a
decreasing trend in dominance in small mammal communities.
Decreasing trends of some generalist northern
species with restricted ranges may have been due to
climate change. Diet monitoring of barn owls are thus
valuable tools for both documenting and analyzing finegrained
small mammal responses to global change.
... Whilst field voles require largish areas of rank grassland, wood mice are ubiquitous in lowland rural Britain, including intensive arable land (Corbet and Harris, 1991). Interestingly, field voles are not found at all in Ireland, where barn owls have been recorded feeding on wood mice, house mice and brown rats depending on land use (Cooke et al., 1996). Love et al. (2000) showed that the barn owl's diet in Britain changed significantly between 1974 and 1997, primarily due to a large increase in the proportion of Apodemus spp. ...
Twenty-one years of carefully documented barn owl (Tyto alba) study and release in England by the South Midlands Barn Owl Conservation Group (SMBOCG) have necessitated a re-examination of some of the premises on which such release schemes are judged. Fifteen years after the first releases, the number of independently breeding owls (i.e. breeding ‘wild’ or ‘as though wild’) in a 1200 km2 study area is still increasing sharply and now far exceeds the number released in any one year, with the rate of increase outstripping the cumulative number of release events. Ringing returns indicate that fledged young dispersed further than adults, and that released adults which immediately deserted their release sites were less likely to survive their first 30 days than those staying in the vicinity of their release, where they could take advantage of supplementary feeding. Artificial feeding at release sites led to pellets containing lower liveweight equivalent of wild-caught prey but higher numbers of fledged young. Otherwise, and importantly, no significant difference in survival, mortality, dispersal, foraging success or breeding success was found between wild/independent owls and various categories of released bird. Availability of field vole habitat was not as important for barn owl breeding success as was found in previous studies, with owls able to replace this species in their diet with the less habitat-specific wood mouse. Evidence is provided that starvation was not as important a cause of mortality as has been proved elsewhere. Although barn owl nests often occurred in extreme close proximity, breeding density had no effect on either foraging or breeding success. The possible genetic consequences of barn owl release in Britain are briefly discussed. Very few barn owl release schemes have attempted to prove that their work is worthwhile, so long-term, well-documented studies such as that presented here are vital in establishing some of the principles involved in releasing barn owls into the wild.
... En general, dichos trabajos justifican el método teniendo en cuenta que las egagrópilas producidas por las lechuzas reflejan fielmente su dieta y que los cambios en la dieta demuestran cambios en la disponibilidad de las especies en la comunidad de micromamíferos (Clark y Bunck 1991, Taylor 1994) debido al carácter oportunista del predador (Díaz et al. 1996). Aparte de algunas limitaciones (Saint-Girons y Spitz 1966, Clark y Bunck 1991), éste es un método útil para establecer patrones de distribución y abundancia de micromamíferos a escala geográfica (ej: variaciones en relación a la altitud o latitud, Clark y Bunck 1991, Pérez-Barbería 1991, Moreno y Barbosa 1992, Torre et al. 1996) e incluso paisajística (ej: variaciones entre tipos de cultivos, Cooke et al. 1996, Torre et al. 1997. Sin embargo, la interpretación de los patrones de riqueza a dichas escalas puede ser dificultosa si no se tiene en cuenta el esfuerzo muestral realizado (Rahbek 1995). ...
Geographic trends in the diet of the common barn-owl (Tyto alba, Scopoli 1769) and the interpretation of patterns of richness of small mammal communities: a new analithical approach We propose the Analysis of Covariance (ANCOVA) as an alternative to the analysis of spatial patterns of richness (ex: index, rarefraction, etc.), a statistical technique that allows the detection of patterns after controlling for the effects of sampling effort on species-richness, one of the most influential biasing factors in these studies. We studied geographic patterns of richness of small mammal communities found in common barn-owl (Tyto alba) dietary studies conducted in Spain. We detected sample biases in all papers analysed, since richness-sample size relationships were linear and explained a great amount of variance (between 43 and 65%). Many studies rarely take account of sample sizes, and conclusions about richness of small mammal communities at spatial scales could be misunderstanding. As a whole, the
... Previous studies of dietary response of T. alba generally were based on pellet contents without assessing availability of prey (e.g., Goutner and Alivizatos 2003; Pardinas and Teta 2005; Leonardi and Dell'Arte 2006; Charter et al. 2009; Platt et al. 2009 ). It was sometimes assumed that pellet analysis provided a reliable indication of the proportion of vertebrates in the field (Taylor 1994; Cooke et al. 1996). This implies that prey diversity in the diet of T. alba directly reflects the community structure and composition of small mammals, and so T. alba capture prey randomly (Ba et al. 2000). ...
The diet of the Barn Owl (Tyto alba (Scopoli, 1769)) was studied over an 8-year period in the Jura mountains of France, during two population surges of its main rodent prey (common voles, Microtus arvalis (Pallas, 1778), and European water voles, Arvicola terrestris (L.,1758)), allowing us to test whether T. alba is an opportunistic predator as is often cited in the literature or exhibits more complex patterns of prey selection as is reported in arid environments. Small mammals were sampled by trapping and index methods. We observed (i) significant correlations between the proportions of A. terrestris, M. arvalis, and woodland rodents in the diet and their respective densities in the field; (ii) interactions between populations of A. terrestris and M. arvalis, indicating that the proportion of each species in diet was affected by the density of the other; (iii) proportions of red-toothed shrews (genus Sorex (L., 1758)) in the diet did not correlate with their abundance in the field, indicating that those species were likely to be preyed upon when others were no longer available. This confirms that T. alba is generally opportunistic; however, prey selection of a focal species (e.g., Sorex spp., grassland species) can be affected by the density or availability of the other prey species.
... od Mice in pellets. Shawyer (1998) also confirmed that there are occasions when Wood Mice can outnumber Field Voles in the Barn Owl's diet, particularly in eastern England and the Midlands. Interestingly, Field Voles are absent in Ireland, and Barn Owls there have been recorded feeding on Wood Mice, House Mice and Brown Rats, depending on land use (Cooke et al . 1996). On the Isle of Man, where Field Voles are also absent, Shawyer (1998) recorded finding Wood Mice occupying grassy habitats which in mainland Britain would be considered more suitable for Field Voles. ...
Capsule This study examines the relationship between habitat variables and various aspects of breeding and foraging performance for 257 Barn Owl breeding attempts involving both released and wild birds, at 86 different nest‐sites over a 14‐year period.Aims The study aimed to: (1) provide evidence for or against the importance of foraging habitat in Barn Owl breeding performance; (2) enable identification of areas which can, and those which cannot, be expected to sustain Barn Owl populations; (3) inform the compilation of any future guidelines such that Barn Owl release schemes are more likely to succeed; and (4) allow the revision of untested concerns in terms of the likely survival or otherwise of Barn Owls in a given area.Methods Three data sources are used to assess the proportions of various habitat types and lengths of linear features in the vicinity of each nest: (1) The Centre for Ecology and Hydrology Land Cover Map; (2) Ordnance Survey Strategi dataset; and (3) Agricultural Census data. These are linked to various aspects of breeding performance.Results Despite the size of the dataset, the number of significant correlations between habitat type and aspects of Barn Owl breeding success was similar to that expected by chance. Sites with more unimproved grassland within 1 km of the nest did not differ from those with less, except by a significant advancement of first‐egg date.Conclusion The paucity of significant results may be evidence that Barn Owls are in fact rather catholic and adaptable in their habitat requirements, and not as dependent upon large areas of Field Vole (or other) habitat as has often been stated.
... Furthermore, changes in diet as seen in pellets reflect real changes in availability of small mammal species (Clark and Bunck 1991). In spite of some limitations (Clark and Bunck 1991; Saint-Girons and Spitz 1966), this method has been successfully used to study patterns of small mammal distribution at a geographical scale through gradients of elevation or latitude (Alegre et al. 1989; Clark and Bunck 1991; Moreno and Barbosa 1992; Torre et al. 1996), and at the landscape or land-use scales (Cooke et al. 1996; Torre et al. 1997). For genet scats, we used information published on the area (Arrizabalaga et al. 2002; Flaquer et al. 2001), adding 11 new sampling places, for a total of 42 latrines scattered along a gradient of 130–1,000 m elevation (elevation 489 6 27 m). ...
Analysis of pellets of Tyto alba and scats of Genetta genetta and Sherman livetrapping were compared to assess richness and composition of small mammal communities in a Mediterranean area (NE Spain). Owl pellets provided 17 small mammal species (17,232 individuals), genet scats 14 species (2,145 individuals), and livetrapping 9 species (1,488 individuals). Owl pellets oversampled insectivores and grassland rodents and undersampled tree-dwelling and woodland rodents. Genet scats and livetrapping oversampled woodland rodents and undersampled insectivores and grassland rodents. After controlling for sample size and elevation differences between methods by means of analysis of covariance (ANCOVA) and rarefaction, owl pellets contained higher richness for small samples (<50 individuals), and scats contained higher richness for large samples (>100 individuals), both having higher richness than livetrapping regardless of sample size. We concluded that both indirect methods provided complementary information of small mammal communities, detecting the 19 small mammal species known to be present in the study area.
... It is also highly unlikely that there has been a long-term presence of the greater white-toothed shrew in Ireland without it being recorded either as fossil material or as a recent member of the Irish mammal fauna. Previous extensive analyses found no evidence of white-toothed shrews in barn owl and raptor pellets in Ireland (Fairley & Clark, 1972;Fairley, 1973Fairley, , 1984Clark, 1974;Smal, 1987;Fairley & Smal, 1989;Cooke et al., 1996;Foley et al., 2006;O'Connell et al., 2006). More recent surveys from 1997 to 2001 of the bank vole, another introduction to Ireland (Claassens & O'Gorman, 1965) also failed to record the presence of the greater white-toothed shrew, despite good coverage of Tipperary and Limerick (Meehan, 2005). ...
Skeletal remains of greater white‐toothed shrew Crocidura russula were recovered from barn owl Tyto alba and kestrel Falco tinnunculus pellets collected at 15 locations in Counties Tipperary and Limerick in Ireland in September 2007 and March 2008. Seven greater white‐toothed shrews were trapped at four locations in Tipperary in March 2008. This is the first Irish record of C. russula and compelling evidence that the species is established in Ireland.
The absence of C. russula from earlier surveys of owl pellets and small mammals in Ireland suggests a recent introduction by uncertain means, possibly since 2001. It seems likely that C. russula will expand its range in Ireland. Its impact on the ecology of habitats in which it is found is uncertain but may be considerable.
... The Barn Owl is a typical raptor in western France, avoiding large forest areas but hunting in both open field and dense hedgerow network landscapes. It is known to be a generalist predator focusing almost exclusively on small mammals, and numerous works pointed out the advantages of analyzing the pellets of this raptor in various ecological research involving small mammals ( Cooke et al. 1996). Nevertheless, the use of pellet contents as estimates of prey proportions in the field depends on the assumptions that owls hunt at random and that the pellets are a random sample of their catch. ...
We studied the response of the small mammal community (rodents and shrews) to recent changes in agricultural systems of western French landscapes. Work was conducted on twelve sites representative of the diversity of farming systems in this region. The characteristics of small mammal assemblages in each site were assessed using Barn Owl (Tyto alba) pellet analysis. Relationships between small mammal data and landscape descriptors were performed through co-inertia analysis. Richness and specific composition of the small mammal community were not affected by the degree of cultivation but variations in species frequency could be observed. The prevalence of some species allowed us to distinguish three main assemblages which were characteristic of low, medium, and high intensified landscapes. Status and life traits of these species showed that intensification of agriculture has negative effects on density of rare and habitat-specialist species while it favours habitat-generalist species, some of them being known to exhibit fluctuating density. The two main ways of agricultural intensification (maize vs. other crops) did not show any significant relationships with species assemblages. Our results gave us the opportunity to suggest recommendations on agronomical and conservation problems that may arise from these changes of agriculture in western France.
... Small mammal occurrence and abundance were estimated at 12 of the 14 sites by analyzing Barn owl (Tyto alba) pellets. The Barn owl is a generalist predator focusing almost exclusively on small mammals without marked selective behavior ( Giraudoux et al., 1990;Cooke et al., 1996;Yom-Tow and Wool, 1997). Thus, pellets composition allowed to compare small mammal diversity at the different sites. ...
Understanding the dynamics of biodiversity in changing agricultural landscapes is a goal for nature conservation and agricultural policies. Agriculture operates at several spatio-temporal levels from field to landscape, and induces differential response of communities according to their ecological traits. Reactions of several taxa to landscape and agricultural changes was conducted along landscape gradients in northern Brittany (France) gathering 14 sites. Landscapes ranged from fine grained areas, with a large proportion of permanent grasslands, wood and hedgerows, to coarse grained ones dominated by crops. Response of communities were either loss of species along the gradient (as for Diptera Chironomidae and Empididae), replacement (Coleoptera Carabidae) and no change in species composition (small mammals). In this paper, we present why these taxa react in such different ways according to their life history traits, their mobility patterns and to which parameters of landscape structure or agriculture intensification they are sensitive. Density of hedgerow networks, and permeability of individual hedgerows determine the spatial distribution of adults Diptera according to their flying ability. Mean body size of carabid beetles significantly decreases along the gradient of agricultural intensification, small species adapted to disturbance replacing large ones that are characteristic of stable habitats. The same small mammal species are found all along the two gradients, but their relative abundance is linked to the importance of crops versus more stable habitats in the landscape. We concluded that species survival in those fine grained agricultural landscapes depends on processes operating at the site scale and defining habitat quality, and processes operating at the landscape and/or metapopulation scale such as landscape modifications in connectivity and habitat availability.
Jaška P. 2023: The Barn Owl (Tyto alba) belongs to iconic species of the Czech countryside. During the 20th century the species declined dramatically and disappeared from many regions, especially at medium altitudes. Today it is listed in the National Red List of Threatened Species as critically endangered. The decline is caused by many factors. Intensification of agriculture and loss of safe breeding sites are the most crucial. In Central Europe, the Barn Owl feeds mainly on the Common Vole (Microtus arvalis) and the prey population cycle affects reproductive success of the owls. The Barn Owl helps in agricultural pest management. It requires diverse farmland habitats with lots of tree lines, hedgerows, old orchards and ditches. Such fine-scale landscape patchwork has a stable water regime, supports species diversity and also attracts people for free time activities. The charismatic Barn Owl with its role in crop protection, dependency on farms for breeding and preferences for diverse agricultural habitats is an ideal umbrella species for countryside wildlife conservation. In spite of all these facts, there is no official national or local action plan for the Barn Owl conservation in the Czech Republic. This paper summarises the most important knowledge about the Barn Owl which is relevant for systematic conservation effort and proposes the rules for such activities at the national or local scale.
Fossil evidence indicates that owls have been preying on bats from as far back as the Pleistocene. Overall, bats form quite small portions (i.e. trace to 0.2%) of the diets (by prey frequency) of European owls. An assessment of dietary studies and anecdotal accounts reveals that five species of European owls, the Eurasian scops owl Otus scops, Pygmy owl Glaucidium passerinum, Tengmalm’s owl Aegolius funereus, little owl Athene noctua and Ural owl Strix uralensis, rarely feed on bats (with less than 0.1−0.4%) and a further two species, short-eared owl Asio flammeus and eagle owl Bubo bubo, may only take bats occasionally, while three species, long-eared owl Asio otus, barn owl Tyto alba and tawny owl Strix aluco, feed on bats more frequently. In this study, a total of 19,864 recorded bats have been preyed upon by these owls, with as many as 48 bat species being identified. Barn and tawny owls have captured most of this total (47.1 and 41.9%), followed by the long-eared owl (7.6%), while short-eared and eagle owls take similar amounts of bats (1.1 and 1.7%, respectively). Owl predation on bats deserves future research because it may help contribute to our knowledge on bat biodiversity and distribution and possibly identify an additional risk for small populations of endangered bats.
Little was known about the small mammal fauna of the Marcal Basin to date, therefore we collected 1,144 Barn Owl pellets from 15 locations in 2017. After the analysis of the pellets, remnants of 3,063 prey items were identified, of which 97.5% were small mammals, belonging to 21 species, while the remaining 2.5% were birds, frogs and insects. Mammal prey items consisted of Cricetidae 41%, Muridae 31% and Soricidae 28%, and in some samples, we found the remnants of European Mole (Talpa europaea), Kuhl's Pipistrelle (Pipistrellus kuhlii), Hazel Dormouse (Muscardinus avellanarius) and Least Weasel (Mustela nivalis). Small mammal species were classified into four functional groups based on their preferences for urban, open, forest or wetland habitats. We investigated whether their relative abundances match with the proportions of the four habitat types in the assumed Barn Owl hunting ranges (cca. 2 km radius circle) in five sample sites. The relative abundance of small mammal species preferring urban habitats showed concordance with the proportion of the appropriate habitat types in the hunting area in two samples, while such concordance was proved for species favouring open, forest and wetland habitats just in one out of five samples. Small mammal functional groups represented in the prey composition do not directly correspond to the proportion of their typical habitats. We conclude that the abundance of various prey types is not suitable for characterising the landscape within the Barn Owl's hunting range.
Capsule: We present a review of the propensity to eat amphibians in the Barn Owl Tyto alba in Europe. Based on the analysis of 596 published studies reporting 3.32 million prey items identified in pellets, 17 869 amphibians (0.54%) were found. An analysis of 9036 amphibians identified to the species level showed that Barn Owls avoid consuming toxic species, and they are able to capture tree frogs (Hylidae) only rarely. The true frogs (Ranidae) are by far the most frequently captured amphibians followed by spadefoot toads (Pelobatidae) and Parsley frogs (Pelodytidae).
Capsule We report a review of the occurrence of bats in the Barn Owl diet Tyto alba in Europe. Based on 802 studies reporting 4.02 million prey items identified in pellets, 4949 were bats (0.12%). We found that bat predation decreased during the last 150 years, is more frequent on islands than mainland, and is higher in eastern than western Europe and in southern than northern Europe. Although Barn Owls usually capture bats opportunistically, they can sometimes specialize on them.
In our research we studied the diet composition of barn owl Tyto alba and long-eared owl Asio otus, which are to be found in the region of the Central Pomerania in northern Poland. Small mammals prevailed in the diet of both species, accounting for more than 90% of their prey. The long-eared owl preyed mainly on rodents (91.1%), and in small numbers on shrews (0.5%). The diet of barn owl was more diversified because in addition to rodents (67.4%) it consisted to a significant extent of insectivora (31.4%). There were, however, considerable dissimilarities in the diet composition of barn owls coming from three different posts, which can be explained by the different hunting areas, and above all by the seasonal differentiation of the owls' presence. The most frequent victims of the long-eared owl were short-tailed voles Microtus arvalis and common voles Microtus agrestis. In the case of barn owls the most frequent victims were short-tailed voles and common shrews Sorex araneus. Birds and amphibians contributed in very small numbers to the diet of both owls – 1.1% for barn owl and 0.5 % for long-eared owl. Insects were found only in the pellets of the long-eared owl. It was dung beetle Typhaeus typhoeus, a species figuring on Polish Red Data Book of Animals, Invertebrates.
Like many states in the European Union, Ireland has yet to fully commit itself to genetically modified (GM) crop technology. The general position of the Irish Government is 'positive but precautionary'. However, with the European-wide de-facto moratorium on commercial production of GM crops now ended, many strategically important decisions regarding the commercial deployment of such crops and their co-existence with conventional/organic crops need to be considered. To date, little research on the environmental impact of GM crops has been carried out in Ireland, and the provision of relevant local information lags far behind that available in other countries in the European Union. In this paper, we discuss much of the new ecological and economic data that have emerged since the moratorium on GM crops was introduced in 1998, assess the likely impacts of pest-oriented GM crops should they be introduced to Ireland and examine criteria for post-release monitoring. We also describe the likely commercial demand for these crops and the consequent priorities for ecological research. We argue that the impact of GM technology needs to be assessed in relation to the environmental impact of modern agriculture as a whole. Public unease in relation to this technology may be addressed if adequate resources are made available for independent Irish research on the issue.
The aim of this study is to compare biodiversity in contrasted landscape units within a small region. In western France agricultural intensification leads to changes in landscape structure: permanent grasslands are ploughed, fields enlarged and surrounding hedgerows removed or deteriorated, brooks are straightened and cleaned. South of Mont Saint Michel Bay, four landscape units have been identified along an intensification gradient. Several taxonomic groups (small mammals, birds, insects and plants) have been used to evaluate the characteristics of biodiversity along this gradient. The hypothesis that intensification of agricultural practices lead to changes in biodiversity has been tested. Biodiversity is measured by the species richness, Shannon's diversity index, equitability and similarity indexes. Our results show that intensification of agriculture does not always lead to a decrease in species richness, but to several functional responses according to taxonomic groups, either no modification, or stability by replacement of species, or loss of species. For most of the studied taxonomic groups species richness does not vary greatly along the gradient. Depending on the landscape structure and farming systems this gradient is probably truncated and does not allow to show major changes in species richness. An alternative hypothesis is that used indexes are not sensitive enough to reveal changes in biodiversity. Nevertheless, similarity indexes reveal that sensitivity to changes varies, invertebrates being more likely to perceive the dynamics of the landscapes studied than vertebrates or plants. These points have to be taken into consideration when elaborating policies for sustainable agriculture or nature conservation.
Mus musculus are poor competitors, and occur largely in association with man, rarely found away from buildings on mainland Ireland, though the opposite is true on offshore islands where the species can thus be said to be truly feral. When man leaves, house mice become extinct where field mice Apodemus sylvaticus are present.-P.J.Jarvis
The diet of the Barn Owl in Ireland was investigated from pellet collections containing a total of 8229 individual prey items. The pellets were obtained from 15 roosts, 6 of which were within the established range of the Bank Vole Clethrionomys glareolus, a recent introduction to the island. Barn Owls were found to feed principally upon rodents, which formed 90% of prey weight consumed and, as in previous Irish studies, Field Mice, House Mice and Brown Rats were important prey items. The Bank Vole was a significant prey species where it occurs, constituting 15–22% of the diet. Other items such as Pygmy Shrews, birds and frogs were generally of seasonal or local importance only. The Barn Owl is an opportunistic feeder specializing in small mammals.