Trends in North American small mammals found in common barn-owl (Tyto alba) dietary studies

Abstract

Data on mammals were compiled from published studies of common barn-owl (Tyto alba) pellets. Mammalian composition of pellet samples was analyzed within geographic regions in regard to year, mean annual precipitation, latitude, and number of individual mammals in the sample. Percentages of individuals in pellets that were shrews increased whereas the percentages of rodents decreased with greater mean annual precipitation, especially in northern and western areas of North America. From the 1920s through 1980s, in northern and eastern areas the percentage of species that was shrews decreased, and in northern and central areas the percentage of individuals that was murid rats and mice increased. Human alterations of habitats during these seven decades are postulated to have caused changes in available small mammals, leading to changes in the barn-owl diet.

Barn owl (Tyto alba) predation on small mammals and its role in the control of hantavirus natural reservoirs in a periurban area in southeastern Brazil

“…Despite being restricted to a single area and based on few individuals, the present study allowed the inventory of eight species of small mammals in Uberlândia. Based on previous studies, small mammals are the main prey of the barn owl, with the relative frequency of rodents varying from 64.1 to 95.8% (Jaksic et al, 1982;Clark and Bunck, 1991;Ebensperger et al, 1991;Love et al, 2000;Corrêa and Roa, 2005;Escarlate-Tavares and Pessoa, 2005). In the study area, small mammals also constituted most of the diet of the species, represented mainly by muroid rodents (85.2% of the prey).…”

“…Possible factors that could explain these changes include differences in habitat types, in relative abundance of small mammal species and/or in statistical distribution of prey size classes (Jaksic et al, 1982). Along its distribution, the barn owl may consume commensal rodents, however, their frequency in the diet is usually low (Clark and Bunck, 1991). Despite the present study having been conducted in an anthropic area, the consumption of M. musculus (n = 9) and R. rattus (n = 2) was rare.…”

“…Studies on the feeding ecology of the barn owl, Tyto alba (Scopoli, 1769), are common and worldwide, particularly in Europe and North America (Hamilton and Neill, 1981;Jaksic et al, 1982;Clark and Bunck, 1991;Torre et al, 1997;Love et al, 2000). This high frequency of studies is due mainly to the wide distribution of the species and to the habit of owls to regurgitate compact pellets with well preserved prey remains, usually under shelters or nests (Sick, 1997;Motta-Júnior and Alho, 2000;Bonvicino and Bezerra, 2003;Corrêa and Roa, 2005).…”

“…Small mammals, especially rodents, are the main prey of the barn owl (Jaksic et al, 1982;Ebensperger et al, 1991) and its diet is considered an accurate reflection of the local fauna composition and populational fluctuation (Clark and Bunck, 1991;Love et al, 2000). Regurgitated pellets of the barn owl have been studied for a long time (Pearson and Pearson, 1947;Jaksic et al, 1982;Pardiñas and Cirignoli, 2002), not only for describing the diet and trophic relationships with other predatory species (Ebensperger et al, 1991;Corrêa and Roa, 2005), but also focusing the richness and relative abundance of small mammals (Jaksic et al, 1982;Pardiñas and Cirignoli, 2002;Bonvicino and Bezerra, 2003;Escarlate-Tavares and Pessoa, 2005), patterns of geographical distribution (Barbosa et al, 1992;Torre, 2001), and temporal changes in prey communities (Clark and Bunck, 1991;Love et al, 2000).…”

Gloger's rule in North American Barn Owls

“…In both Switzerland and Israel, dark reddish owls are mainly found in fields, and white owls close to forests, something that could explain why dark and pale reddish Barn Owls have a different diet in these two countries (Roulin 2004b, Charter et al 2012, Dreiss et al 2012. Because Barn Owls in the USA consume more shrews and fewer rodents in regions where it rains more (Clark and Bunck 1991), it is possible that the association between reddish coloration and climate may be driven by predator-prey relationships. If the predatorprey relationship is the main selective agent in the Barn Owl, whereas climate exerts the most selective pressure in other owls, this could explain why cline variation in the degree of pheomelanin-based coloration in the Barn Owl does not follow the general pattern observed in other owls.…”