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The diet of the Barn Owl in central Chile and its realation to the availability prey
... Avery, Avery, & Palmer, 2005;Bernard et al., 2010;Flikweert et al., 2007;Herrera, 1974;Love, Webon, Glue, Harris, & Harris, 2000;Taylor, 2004), but other studies have shown considerable differences between prey composition in the pellets and that recorded using trapping data in the field (e.g. Jaksić & Yáñez, 1979;Marti, 1974;Perrin, 1982;Yom-Tov & Wool, 1997; see also Heisler, Somers, & Paulin, 2016 for a multispecies study). In addition, experimental studies under controlled aviary conditions have also shown that barn owls select prey according to their size, activity and vulnerability (e.g. ...
Aim. The investigation of biogeographical patterns in the diet of widely distributed predators is essential to understand their ecology, life-history traits, and local adaptations. However, it is particularly challenging because of their wide distribution, broad trophic spectra and high ecological plasticity. Here, we described patterns of trophic ecology in a cosmopolitan nocturnal raptor, the common barn owl group, from a biogeographical perspective. We then compared variation in diet between barn owls living in the Americas (T. furcata), and those inhabiting in Europe, Middle-East and Africa (T. alba), thus hunting on different assemblages of prey types.
Location. World.
Taxon. Barn owl species complex.
Methods. We reviewed 790 studies reporting diet information of 971 locations (3,733,902 individual vertebrate prey), and investigated the variation in different diet parameters, reflecting taxonomic diversity, size of the prey and frequency of certain prey types according to geographic and climatic variables.
Results. While confirming that the barn owl is a selective mammal hunter with variable taxa constituting its staple food in different regions, we also found significant geographic and climatic trends in several diet parameters. Although prey composition differed among continents, most of the patterns, including an increase of proportion of mammal prey in cold environments, an increase in diet diversity with elevation, a decrease in small prey consumption from high to low latitudes and at increasing temperature, and a decrease in rodent predation in humid habitats, were similar between T. furcata and T. alba. A strong island effect was observed for all diet parameters.
Main conclusion. Our results indicate a generalized pattern of variation in barn owl diet across biogeographic regions, suggesting that similar prey communities occur in habitats with comparable ecological conditions and/or that different barn owl populations living in similar climate convergently evolved similar food preferences and hunting strategies.
... Finalmente parecieran compensar el tamaño de sus presas con la abundancia de estas para sa sfacer sus requerimientos energé cos (Jaksic et al. 1981, Jaksic 1997, Rau et al. 2005, Figueroa et al. 2009, Muñoz-Pedreros et al. 2010). Péfaur et al. (1977) y Jaksic & Yáñez (1979) señalaron que los estrigiformes depredan sobre los roedores en dis nta proporción a la disponibilidad ambiental. Esto se ha corroborado para la RN Lago Peñuelas, Valparaíso (Muñoz-Pedreros et al. 2010, 2016 y para Burca, Concepción (Muñoz-Pedreros & Murúa 1990). ...
... In general, the diet of the Chilean population of Barn Owl is composed mainly of small mammals, particularly noct u r nal rodents (Jaksic and Yáñez, 1979;Cerpa andYáñez, 1981, Jaksic et al., 1981), although other important items are marsupials, birds and ar thropods. The diet of this raptor has been st udied in many Chilean locations, such as Chiu-Chiu, Antofagasta region (Jaksic et al., 1999), La Dehesa, Metropolitana region (Reise, 1970); Fray Jorge, Coquimbo region (Schamberger and Ful k, 1974); Puchuncaví (Cerda a nd Yá ñez , 1981) and La Campana (Zu nino and A rcos, 1989) both in Valparaíso region; Lastarria, A raucanía region (Rau et al., 1985); Ter mas del Flaco, Libertador Bernardo O'Higgins region (Tor res-Mura and Contreras, 1989); Burca, Concepción region (Muñoz and Murúa, 1990); Torres del Paine, Magallanes region (Iriarte et al., 1990); ...
The Barn Owl (Tyto alba) is a nocturnal raptor species distributed from Arica to Tierra del Fuego in Chile. The diet of this bird is the best known of any raptor of Chile; it is based on small vertebrates, particularly rodents and birds. We studied the diet of the Barn Owl, by analyzing of pellets collected in Copiapó valley, located in the hyper-arid Atacama Desert. This information was compared to available data from Chile and neighboring countries. Because of the environmental conditions of extreme aridity a low diversity of prey, typical of raptors from arid ecosystems, was expected. In the case of Tyto alba populations from the Atacama region, the most consumed species were rodents (76.7%), specially Eligmodontia dunaris (27.3%), Phyllotis darwini (24%) and Abrocoma bennetti (12.4%). Other preys corresponded to birds (17.8%) and coleopterans (3.3%). There was no significant correlation between frequency of prey and their body mass (r2= 0.229, p= 0.497) and between frequency of prey and their habitat (r2= 0.538, p= 0.088), indicating that this raptor does not select its preys by either body size or habitat. Regarding biomass, rodents contributed more significantly (95.3%) than birds (3.5%), with the largest individual contribution given by A. bennetti (60.1%) and P. darwini (26.8%). Both the Simpson (SI = 0.1683) and Shannon (H’= 0.8958) indices indicate that this species consumes a low diversity of prey, which is consistent with the observations for others raptors inhabiting on arid environments.
... Tyto furcata seems to overconsume or under-consume some small-mammal species in relation to their field abundance (Jaksic 1979Jaksic and Yáñez 1979;Simonetti and Walkowiak 1979;Jaksic et al. , 1992Jaksic et al. , 1997Iriarte et al. 1990;. A most recent study conducted in Lago Peñuelas, central Chile, appears to confirm prey selection by this owl species. ...
To achieve a better understanding of the life histories of Chilean owls and to generate a useful source of information for future studies, we undertook an exhaustive review of all available information relating to their taxonomy, natural history, ecology, genetic and conservation biology. Studying these topics we gathered information on morphology, morphometrics, distribution, abundance, habitat, reproduction, longevity, behaviour, diet, feeding ecology, population ecology, community ecology, functional ecology, ecophysiology, endemism, conservation status, threats, human perception, legislation, education and outreach, physical rehabilitation, and habitat management. During our review, we rediscovered and retrieved naturalist’s observations that had remained totally unknown to contemporary ornithologists. Some of the challenges that must be addressed to achieve a clearer understanding of the biology of Chilean owls and strengthen conservation strategies are (i) to definitively determine the validity of Bubo magellanicus as a separate species and establish the true extent of its distributional hiatus; (ii) to determine the geographic boundaries for Glaucidium nana and G. peruanum; (iii) to detect the ocurrence of population size variations and to identify possible causal factors; (iv) to identify variables that promote the use of, and preference for, habitats; (v) to ascertain, in detail, their reproductive characteristics, home ranges, and dynamic movements; (vi) to assess their diets in poorly studied ecosystems; (vii) to determine their relevance in local food webs and roles in ecosystems; (viii) to evaluate the genetic structure of owls in highly fragmented landscape; and (ix) to promote much more education about their natural history. We think that our review will be useful both in guiding new conservation efforts and opening new research perspectives that will help fill information gaps.
... In general, the diet of the Chilean population of Barn Owl is composed mainly of small mammals, particularly noct u r nal rodents (Jaksic and Yáñez, 1979;Cerpa andYáñez, 1981, Jaksic et al., 1981), although other important items are marsupials, birds and ar thropods. The diet of this raptor has been st udied in many Chilean locations, such as Chiu-Chiu, Antofagasta region (Jaksic et al., 1999), La Dehesa, Metropolitana region (Reise, 1970); Fray Jorge, Coquimbo region (Schamberger and Ful k, 1974); Puchuncaví (Cerda a nd Yá ñez , 1981) and La Campana (Zu nino and A rcos, 1989) both in Valparaíso region; Lastarria, A raucanía region (Rau et al., 1985); Ter mas del Flaco, Libertador Bernardo O'Higgins region (Tor res-Mura and Contreras, 1989); Burca, Concepción region (Muñoz and Murúa, 1990); Torres del Paine, Magallanes region (Iriarte et al., 1990); ...
The Barn Owl (Tyto alba) is a nocturnal raptor species distributed from Arica to Tierra del Fuego in Chile. The diet of this bird is the best known of any raptor of Chile; it is based on small vertebrates, particularly rodents and birds. We studied the diet of the Barn Owl, by analyzing of pellets collected in Copiapo valley, located in the hyper-arid Atacama Desert. This information was compared to available data from Chile and neighboring countries. Because of the environmental conditions of extreme aridity a low diversity of prey, typical of raptors from arid ecosystems, was expected. In the case of Tyto alba populations from the Atacama region, the most consumed species were rodents (76.7%), specially Eligmodontia dunaris (27.3%), Phyllotis darwini (24%) and Abrocoma bennetti (12.4%). Other preys corresponded to birds (17.8%) and coleopterans (3.3%). There was no significant correlation between frequency of prey and their body mass (r(2)=0.229, P=0.497) and between frequency of prey and their habitat (r(2)=0.538, p=0.088), indicating that this raptor does not select its preys by either body size or habitat. Regarding biomass, rodents contributed more significantly (95.3%) than birds (3.5%), with the largest individual contribution given by A. bennetti (60.1%) and P. darwini (26.8%). Both the Simpson (SI = 0.1683) and Shannon (H'=0.8958) indices indicate that this species consumes a low diversity of prey, which is consistent with the observations for others raptors inhabiting on arid environments.
From October 2001 to June 2004, studies were conducted on the Forest Owlet (Heteroglaux blewitti) to evaluate its ecological requirements. A status survey was conducted in ten protected areas of Maharashtra from February to June 2004. A call count method was found useful for detection of the Forest Owlet. During this survey 98 individuals of the Forest Owlet were observed in Maharashtra. Of these 79 were found in Melghat Tiger Reserve (MTR) and 19 individuals were found in Toranmal reserve forest.
Point centered quarter method (n=70) shows preference of the open type of Teak dominated forest by the Forest Owlet. Similarly, Circular plot method has shown difference between roosting, nesting and foraging plots. Direct observations and pellet analysis reveal that the rodents, skink and agamid are the major prey items of the Forest Owlet. Effect of rainfall and bamboo flowering on the diet shift was also observed. Data were obtained on courtship, nest requirements, clutch size. The Forest Owlets are having prolonged breeding season from October to May. The hatching success is 59% and the overall fledgling success is 41%. Predation of fledglings, egg removal from nest, ovicide and infanticide are the major factors influencing the overall breeding success of the Forest Owlet.
Encroachments, increasing use of pesticide and rodenticides, illicit woodcutting, grazing and superstitions among tribal are influencing the survival of the Forest Owlet. Community management, joint forest management and public awareness are the key factor in long term conservation of the species.
The trophic ecology of five owl species was studied in some areas of central São Paulo
State through pellet analysis. The most important prey as small mammals, birds, and insects were monitored by trapping procedures between 1992 and 1993. Pellets were collected between 1985 and 1994, but prey selection analysis was performed only for simultaneous pellet and prey samples.
The analysis of the number of individual prey items reveals that the smaller owl species,
Athene cunicularia (the Burrowing Owl, 145-185 g) and Otus choliba (the Tropical Screech Owl, 118-141 g) feed mostly on insects and other arthropods. The food of Barn Owl (Tyto alba, 360-480 g) is composed by insects and small rodents in similar proportions. The largest species, Rhinoptynx clamator (the Striped Owl, 347-546 g) and Asio stygius (the Stygian Owl, 633 g) feed on vertebrates, particularly rodents and marsupials for the former, and mostly birds for the latter.
The analysis of total the estimated biomass consumption shows that rodents represented
the bulk of A. cunicularia and T. alba food habits. Otus choliba and the two largest species have no significant changes in their diets when biomass consumption and number of individuals are compared.
Most insects are more preyed on rainy and warm months, while rodents are captured in
the dry and cold season. This pattern fits with the natural cycles of abundance of the prey
suggesting an opportunistic feeding behavior by the owl species.
On the other hand, the owls select rodents and birds according to species, age and size.
Apart from R. clamator, which feed on several medium sized birds and rodents, all the other owls catch smaller prey. Asio stygius seems to be centralized in the predation of small granivorous and gregarious birds (mostly Volatinia jacarina, 9.8 g) living in grasslands. Tyto alba and A.cunicularia select the smallest rodents (Calomys tener, 7.7-14.3 g; and Oryzomys nigripes, 7.3-17.2 g) in relation to the more common and larger Bolomys lasiurus (18.0-42.4 g). Furthermore, selection of the smaller rodents does occur within species, including especially juveniles and subadults. The displacement in social hierarchy of juvenile/subadult individuals promotes dispersion into unprotected areas without vegetation cover. Thus, non experienced individuals can be more easily capture by owls. The choice for the small individuals between and within rodent species appears to
contradicts one of the predictions of the Optimal Foraging Theory, which states that a predator should select only the most valuable prey in energetic content. On the other hand, two other predictions are partially in accordance with the field data. One of those states that when the prey abundance declines, the overall diversity of the diet should increase. This occur in the rainy season, when rodents are rare and the insects constitute the main component of the owl diets.
The other prediction supposes that the inclusion of a prey species in the diet does not depend onits abundance, but only on its own energetic value and on the abundance of prey species of higher energetic values. This is in accordance with the higher consumption of insects in months of lower abundance of rodents (wet season), even though insects are also superabundant in that time of the year.
There are mechanisms of ecological isolation operating in the relationships among owl
species, especially in trophic niches and choice of foraging habitats. The differences do not occur only on proportions of food types in the diet, but also in activity sites of preferential prey. Asio stygius shows the more specialized and dissimilar food habits among all species of owls, mostly preying on Passerines. However, R. clamator does exhibit generalized diet, for several prey types as rodents, marsupials, birds, and insects which are consumed with equitability.
The prey remains from owl pellets are an excellent material for small mammal inventories.
In the study areas were recorded 39 species of mammals, including 17 rodents and 19 bats. The pellets of T. alba provided the first record of the little known rodent Pseudoryzomys simplex forSão Paulo State, southeastern Brazil.
Among all Strigiformes studied A. stygius should be considered the most threatened, for
their populations are very local throughout neotropics, the diet is specialized, and restrict habitats as grassland savannas are utilized in the foraging activities. The owls experience several types of human disturbance which affect their survival. The accumulation of new and basic ecological data about owl species, and the introduction of educational programs emphasizing the role of owls in nature are important steps to the conservation of Brazilian owls.
Studies with individual rodents have revealed that they display protean (unpredictable) behavior when attacked by an owl. Other studies have revealed that voles in groups reduce behavioral variability a short time after owl attack, as if adopting the behavior of the higher-mass and perhaps older and more experienced, individuals. Here, we tested groups of rodents under owl attack in order to track the behavior of individuals within the group and compare between the behaviors of social and non-social species. We found differential behavior between species, between groups of the same species, among individuals in the same group, and among the various phases of the owl attack. We also found that upon being exposed to an owl, social rodents tended to huddle together whereas solitary rodents tended to scatter across the available space. Other non-social but perhaps not necessarily solitary rodent species displayed a mixed spacing, with some huddling and some scattering. The findings of the present study shed light on the defensive dynamics of small groups of social and non-social rodent species when they were under owl attack.
Significance statement
Freezing and fleeing are defensive responses that span the animal kingdom, and rodents display various combinations of these in order to prevent predators from predicting their response. Groups of six voles or six spiny mice that were attacked by a barn owl differentially displayed these responses during various phases of the owl attack. Responses also varied among individuals of the same group and among different groups. Finally, we show that when exposed to an owl and displayed freeze response, individuals of social species tended to huddle together, whereas individuals of solitary species scattered over the arena.
Raptors are important predators of various species of small mammals, which renders them of economic importance since their prey may be either disease vectors or reservoirs which represent health problems, or economically important through the damage they cause to crops and stocks. The long-tailed rice rat Oligoryzomys longicaudatus is a reservoir and vector of Hantavirus, a disease of increasing importance in various Latin American countries. The nocturnal Barn Owl (Tyto alba) and the diurnal White-tailed Kite (Elanus leucurus) appear to be the most significant predators of this species. Here, we characterize the diet of these two raptors and analyze their trophic specialization and dietary selectivity using published information, pellet analysis, and field abundances of small mammals. Both raptor species positively selected O. longicaudatus in their diets to suggest that they could be potential controllers of the Hantavirus reservoir in Chile, both in natural and agricultural ecosystems. Predation on O. longicaudatus by these two raptors is interesting because they have complementary activity periods, a condition which enables them to share the same prey without having strong interference.
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