Owl ecology Research Papers - Academia.edu (original) (raw)

- by
- •
- Natural History, Owl ecology, Owl Conservation

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... more

- by Ricardo Figueroa and +1
- •
- Raptor Biology, Raptor Conservation, Raptor Medicine, Ornithology Raptors Behavioural Ecology

Spirit, Power and Axis of everything, in our mortal eyes there is Emptiness: for the truly complete in these empty ones is empty. The Moon, the Axis of everything in our world, is therefore empty for them, and SHOULD BE empty. // Дух, Сила и Ось всего, в смертных очах — Пустота: ибо истинно полное в них, пустых, пусто. Луна, Ось всего в нашем мире, для них посему и пуста, и ДОЛЖНА БЫТЬ пустой.

- by Oleg Yermakov
- •
- Languages, History, Ancient History, Evolutionary Biology

The assessment of feeding conditions and variations in diet composition over the pre-breeding period of birds plays a key-role in the understanding of reproductive performance. Pellets regurgitated by the Little Owl, Athene noctua, were collected from Boulhilet (Batna, northeast Algeria). The analysis of 48 pellets resulted in the identification of 471 prey-items of 38 different species classified into 6 classes, 7 orders, 21 families and 35 genera. The diet of the Little Owl is very diverse (Food Niche Breadth = 14.5, Shannon index = 4.4 bits), a variety of arthropods account for this diversity. Although insects made up 90% of the food consumed, they accounted only for 8% of the total biomass. Seventy two percent of diet biomass consisted of small mammal prey, which constitute a rich source of energy during the pre-breeding period when other prey are not available due to cold conditions. We found no significant change in rodent availability in the diet (number of prey-individuals, biomass, prey-species richness, prey-species occurrence) among study months and years. Meanwhile, the other identified prey-categories, principally invertebrates (characterized by prey frequency, composition, and biomass) showed significant variations between months and/or years of the study. We suggest that these prey categories represent a food supplement when conditions become severe.

- by Haroun Chenchouni
- •
- Zoology, Ornithology, Animal Behavior, Urban Biodiversity Conservation

Ecology and conservation of Chilean owls: progress and research challenges. – We summarize progress and pending challenges in ecological research and biological conservation of the Chilean owls. Ecological aspects in which substantial or preliminary progress have been made includes ecology at individual, population, community, functional, and behavioral level. Progress in conservation includes approaches on population status, threats, conservation priority, human perception, legislation and protection, rehabilitation, education and outreach, and habitat management and restoration. Main challenges in terms of conservation include (i) completing of autecological information, (ii) initiating of behavioral studies, (iii) evaluate their reproductive performance, (iv) assess its sensitivity to landscape changes, and (v) explore its utility as conservation tools. Such challenges must be addressed from, if possible, both the academic and nonacademic ground (e.g. governmental and non-governmental agencies).

- by Ricardo Figueroa
- •
- Environmental Education, Science Communication, Conservation Biology, Ecology

In this literature review, I examined 475 publications with information on the global diet of the Long-eared Owl Asio otus. Data within 312 publications were entered into a database, and quantitative diet data were available from 194 of these publications. The composite data set identified 477 different prey: 180 mammal, 191 bird, 15 reptile, 7 amphibian, and 1 fish species, and 83 invertebrate groupings. In 798 prey lists reflecting 813 033 prey items, small mammals accounted for 93.3% and birds for 6.4% of the vertebrate prey. Prey ranged from 1–500 g, with the vast majority of prey consisting of species ≤50 g. Twenty-three species predominate the prey in at least one species list. Diet composition at the family level was similar in different regions, but considerable differences were shown at the species level.

- by Simon Birrer
- •
- Feeding Ecology, Owls, Diet Composition, Owl ecology

The Roach’s mouse-tailed dormice (Myomimus roachi) is an endangered
mammal in Europe with poorly known distribution and biology in Bulgaria.
Cranial remains of 15 specimens were determined among 30532 mammals
in Barn Owl (Tyto alba) pellets in 35 localities from 2000 to 2008 and 32941
mammals in Eagle Owl (Bubo bubo) pellets in 59 localities from 1988 to
2011 in SE Bulgaria. This dormouse was present with single specimens in
11 localities and whit 4 specimens in one locality. It is one of the rarest
mammals in the region that forms only up to 1% by number of mammalian
prey in the more numerous pellet samples. The existing protected areas
ecological network covers six out of 15 (40%) localities where the species
has been detected in the last two decades. We discuss the necessity of
designation of new Natura 2000 zones for the protection of the Roach’s
mouse-tailed dormouse in Bulgaria.

- by Boyan Milchev
- •
- Mammalogy, Natura 2000, Pellets, Owl ecology

We quantified the diet of the Rufous-legged Owl (Strix rufipes) by analysing 63 pellets collected during 2003 and 2005 in a small coastal sclerophyllous forest stand at the northern limit of its distribution in Chile (31–32°S). The diet comprised small mammals (frequency = 57.8%, biomass = 99.3%), crustaceans (frequency = 1.7%, biomass = 0.1%), and insects (frequency = 40.5%, biomass = 0.6%). We identified at least 10 small mammal species in these pellets of which Bennett’s chinchilla rat (Abrocoma bennetti; frequency = 12.4%) and long-tailed pygmy rice rat (Oligoryzomys longicaudatus; frequency = 7.4%) were the most frequently occurring mammalian prey remains. Terrestrial small mammals accounted for 21.5% by frequency of all individuals and 49.1% of the total biomass; scansorial/arboreal small mammals accounted for only 13.2% of all individual prey and 17.2% of total biomass.

- by Ricardo Figueroa
- •
- Trophic Ecology, Owl ecology

What future for Tengmalm’s Owl Aegolius funereus in the Jura Mountains ? Thirty years of study reviewed. Tengmalm’s Owl has been studied for over thirty yearswithin an area of 150 km2 in the Jura Mountains in the north of the Canton of Vaud (CH) and the Department of Doubs (F). Six hundred and one nests were studied, of these 176 in Black Woodpecker Dryocopus martius cavities and the remainder in nest boxes. Annually the number of nests varied from 2 (minimum in 2013) and 57 (maximum in 1992), with an average of 20.
Overall there has been a marked reduction in the number of nests to the extent that if this evolution continues it can be expected that the species will have disappeared from the Jura
Mountains between 2025 and 2035.
Eggs are laid from the end of February to the end of June, with large variations from one year to another both in terms of the average and the length of the season. The clutch size varies from
2 to 9 with major differences in the average from one year to another. The actual number depends on food availability but also predation by European Pine Marten Martes martes which
sometimes can be extremely high. All these factors are closely linked. The annual number of nests is closely correlated with early breeding, the number of eggs and a high reproductive success.
The dominant food brought to the young is dominated by three types of prey : Field mice Apodemus are the commonest and are associated with reproductive success. Bank vole Myodes glareolus also plays an important role.
In opposition to this Eurasian shrew Sorex araneus is a common prey item and present when Field mice and Bank voles are lacking.
Eurasian shrew abundance correlates with poor reproductive success.
Capture and control of ringed birds show their considerable nomadism, which varies from one season to another. The majority of adult females and the young leave a sector after an
abundant year. Sedentarity increases and is at a maximum between two abundance peaks.
Multiple factors are probably responsible for the major reduction in the breeding population. Forest management leading to the elimination of old trees and favouring conifers over beech
is probably one of the causes. Competition with Tawny Owl Strix aluco, which is becoming more and more common, in areas where previously it was absent, is also a factor. Global warming
is probably also a factor as it affects other parameters that are essential to the survival ofTengmalm’s Owl in the Jura Mountains.

- by Pierre-Alain Ravussin and +2
- •
- Ornithology, Owls, Owl ecology

The analysis of the pellets belonging to two sympatric owls (long-eared owl Asio otus and barn owl Tyto alba) from the Cefa Nature Park in the northwestern part of Romania) showed a clear predominance of small mammals, in diet of both species. A certain degree of specialization can be noted in the case of A. otus preying preferentially on Microtus arvalis. On the other hand, T. alba, consumes large quantities of common voles and constitutes only 31% of its total food source. Both species consume the occasional bird and represents less than 1% of its total prey. The standard Levins Index of the niche for T. alba (0.37) shows that the trophic niche-width is considerably larger in the case of A. otus (0.17). The barn owl subsists off of a much more diverse diet compared to the long-eared owl (16 vs 9 prey species). The two owl species live sympatricaly, using the same habitats, despite the existence of a considerable dietary overlap, but they avoid competing with each other by using different niches.

- by Attila Sandor
- •
- Ornithology, Owl ecology

This study of the diet of Barn Owl Tyto alba analyzed pellets containing 18,810 prey specimens. Small mammals (98.2%
by number, 97.5% by biomass) dominated, while birds, reptiles, amphibians, and insects constituted a negligible portion of the diet
(1.8% by number, 2.5% by biomass). Voles (Microtus spp.) were the most numerous prey (35.3 ± 14.4%, range 14.6%–67.1%) in 9
localities (69.2%, n = 13 individually studied localities) and dominated the biomass in all diets (51.4 ± 14.1%, range 27.4%–78.2%).
The lesser white-toothed shrew (Crocidura suaveolens) (20.8 ± 7.6%, range 7.3%–32.8%) was the most frequent prey in the other 4
localities (30.8%). The breeding localities with more similar proportions of habitats in their hunting territories had significantly higher
diet overlaps (r = 0.336, P < 0.01). The amount of wetlands and the indices of habitat heterogeneity and topographic relief among
the landscape characteristics of the hunting territories significantly influenced diet composition according to redundancy analysis.
Larger areas of wetlands correlated with higher predation on wetland mammal species, as well as the European pine vole (Microtus
subterraneus) and white-toothed shrews, and thus with broader food niche breadth.

- by Boyan Milchev
- •
- Feeding Ecology, Owl ecology, Hunting Territory, Pellet Analysis

Two localities with unsuccessful breeding of Eagle Owls were found in the Kazanlak Valley (0.25 pair/100
sq. km). Mammals (41.3% by number, 47.9% by biomass) and birds (56.2% by number, 52.0% by biomass)
predominated in the diet among 72 animal taxa. Most important prey species were Erinaceus roumanicus
(7.4% by number, 21.3% by biomass) and Rattus norvegicus (8.8% by number, 7.4% by biomass), within
a broad food niche with a high number of birds. The quantitative parameters of carnivore mammals and
birds (11.5% by number, 20.4% by biomass) were much higher than their mean values in Europe and on
the Balkan Peninsula. The open non-forested lands were the main hunting habitats but wetlands were the
most exploited ones according to their small surfaces in the main hunting area and disproportionate numerous
inhabitants in the diets. The small number of breeding birds, later clutches, higher diet diversity
with considerable share of mesopredators, in the Eagle Owls studied could be a result of decreasing supply
of the preferred prey (following the food stress hypothesis), as well as of inhabiting suboptimal territories
in the valley.

- by Gradimir Gruychev and +1
- •
- Ornithology, Population ecology, Birds (Ecology), Small Mammals

Fragmentation of native forest and woodland by clearing for agriculture and urban development has had a greater effect than logging on large forest owls and their arboreal marsupial prey. In this study, assessments were made of the contribution of forest and woodland fragments on privately-owned and unprotected lands towards the
regional conservation of these species in southeastern New South Wales. Small (<200 ha) frag- ments did not provide a significant reservoir for populations of the Powerful Owl Ninox strenua, Sooty Owl Tyto tenebricosa and Masked Owl T. novaehollandiae. Virtually all records of these owls in the region were associated with extensively forested areas or occurred within one km of the boundary of these areas (mainly state forests, national parks and nature reserves). The Barking Owl N. connivens, a ‘non-forest’ species, was also rarely recorded in forest/woodland fragments, raising concerns about the conservation status of this species in the region. Several important prey species for the three large forest owls, in particular the Common Ringtail Possum Pseudocheirus peregrinus, Greater Glider Petauroides volans and the Sugar Glider Petaurus breviceps, were either absent or less abundant in small forest fragments. The Barn Owl Tyto alba, a woodland species, and two other nocturnal ‘forest’ birds, the Southern Boobook Ninox novaeseelandiae and Australian Owlet-nightjar Aegotheles cristatus, were common and widespread in small forest and woodland fragments.

- by Matthew Stanton
- •
- Landscape Ecology, Zoology, Wildlife Biology, Wildlife Ecology And Management
- by Geoff Lundie-Jenkins
- •
- Owl ecology, Raptors and owls

The population peak of voles (Microtus spp.) in south-east Bulgaria leads to their
dominance – 50.9 ±5.2 % by number and 67.9 ±5.4 % by biomass – in the diet of Barn
Owl (Tyto alba) (n = 9 localities). The average weight of Barn Owl prey increases to
24.7±0.8 g, the food-niche narrows to 2.83±0.3, and the overlap in diets rises to 98 %.
The two taxa, true mice (Mus spp.) and white-toothed shrews (Crocidura spp.), dominate
the diet of Barn Owls under normal conditions at the study sites but have a considerably
lower proportion during spikes in vole population. Together with voles, the true mice
(20.3 ±5 % by number and 18.9 ±5 % by biomass) form 80 % by number and biomass
of the prey. The proportion of little white-toothed shrew (Crocidura suaveolens)
(15.2 ±4.2 % by number and 3.1 ±0.7 % by biomass) declined and the species became
a secondary prey species in terms of prey biomass. The bicoloured white-toothed shrew
(C. leucodon) dropped from the list of important prey species during spikes of vole
population. Farm use of rodenticides is very likely to have caused a decline in the
number of voles and true mice in the diet. The Barn Owl changed its prey target to
white-toothed shrews (41 % and 57 % by number, 20 % and 25 % by biomass), eastern
spadefoot (Pelobates syriacus) (up to 6 % by number) and large (up to 5 cm) grasshoppers
(Decticus albifrons) (up to 6 % by number) as well as to other shrews (up to
10 % by number).

- by Boyan Milchev
- •
- Pellets, Owl ecology
- by Hillel Schwartz
- •
- Owls, Owl ecology
- by Sergio Alvarado
- •
- Conservation Biology, Life history, Ecology, Animal Behaviour

Chaco Owl is a medium-sized owl that is distributed through a 766,000 km2 area of southern South America, from the Chaco region of southern Bolivia (Santa Cruz) south western Paraguay and to Argentina, south to Córdoba and Buenos Aires provinces. This owl inhabits both dense and open forests and shrubs on either hilly, rolling and flat areas. Its diet include small mammals, birds, reptiles, insects, scorpions and centipedes. Chaco Owl is mainly nocturnal and crepuscular, and rests during the day in tree cavities, dense brush, isolated trees or even on the ground. This owl primarily is resident, but some individuals may move seasonally among different habitats. Although considered "scarce", it could be locally common. Although Chaco Owl is not considered to be threatened on the global level, local populations of this species may be vulnerable to habitat changes.

- by Flavio Martinez
- •
- Conservation Biology, Life history, Ecology, Animal Behaviour

Studies of the diet of Barn Owls in South-eastern Bulgaria show that small mammals
predominate, forming 98 % by number and 97 % by biomass. The most important
taxa are mice Mus spp., Lesser white-toothed shrew Crocidura suaveolens, voles
Microtus spp. and Bicolored white-toothed shrew C. leucodon, which form 86 % by
number and 85 % by biomass of the prey. The proportions of birds, reptiles, amphibians
and insects are negligible. Mice Mus spp. predominate in the food in 45 %
(n=20) of the localities by number and in 30 % by biomass; voles Microtus spp. in 20 %
by number and in 70 % by biomass; and Lesser white-toothed shrew C. suaveolens
in 35 % by number. The breadth of the food-niche is 3.14 ± 0.79 (n=20 localities).
The most important type of prey is small mammals of the dry open cultural landscape.
Wetlands provide additional food sources (Neomys anomalus, Micromys
minutus, Arvicola terrestris). The extent of variability of the diet in areas with negligible
proportions of wetlands is determined by mice and shrews (Sorex, Crocidura). A
greater share of shrews in the diet is associated with a decrease of the proportion of
mice and a widening of the food-niche breadth.

- by Boyan Milchev
- •
- OWL, Pellets, Owl ecology

The Barn Owl (Tyto alba) is a common nocturnal predator of agro-ecosystems and it is widely distributed, especially in European countryside. A ﬁ rst assessment of the diet and food selection was made for the Southern part of Danube Delta Biosphere Reserve, in the summer period, in a unique wetland-grassland complex, with large areas of steppes. Mammals dominated the diet spectrum, with the shrews (Soricidae) being the most frequent (49.4 %), followed by the mice (Muridae), and the voles (Arvicolinae). The mammalian component of diet is the most important also in terms of biomass (94.3%), the most important species is Sibling Vole (Microtus epiroticus) equaling 22.5% of all biomass consumed, followed by White-toothed Shrew (Crocidura suaveolens) and the Mound-building Mouse (Mus spicilegus). Birds, reptiles, amphibians and insects made up a small portion of the diet, both in terms of occurrence and of biomass. Eight species of birds were captured, the House Sparrow (Passer domesticus) being the most important. Two species of reptiles and at least four species of amphibians were recorded. Arthropods (at least 9 species) made up to 3.8% of the diet. The results suggest that the Barn Owl is a specialised feeder relying on small mammals and completing its diet with other prey only occasionally.

- by Attila Sandor
- •
- Ornithology, Mammalogy, Birds (Ecology), Owl ecology

Eagle Owls Bubo bubo dust-bathing in ash from car tyres in the open Like other bird species, Eagle Owls take baths in ashes and sand in order to cleanse their skin and plumage. It has now been discovered that, at two breeding sites in south-eastern Bulgaria, Eagle Owls also use the ashes of burnt car tyres for this purpose. The toxic substances in this ash could have negative effects on the owls from these breeding sites. This does not however represent a general threat to the Eagle Owl population, as locations where tyres are burnt illegally are uncommon in Bulgaria. In some developing countries however, where burning of car tyres occurs more frequently, this could prove to be dangerous for dust-bathing birds.

- by Boyan Milchev
- •
- Owl ecology, Raptors and owls

Abstract. MICROVERTEBRATE TAPHONOMY OF THE ARCHAEOLOGICAL SITE CUEVA TIXI (LATE PLEISTOCENE–LATE HOLOCENE) EASTERN TANDILIA (BUENOS AIRES PROVINCE, ARGENTINA). The taphonomic attributes of a sample of microvertebrates composed by 67805 remains, from the archaeological site Cueva Tixi (Eastern Tandilia, Buenos Aires Province, Argentina), were analyzed. Mammals, birds, frogs, snakes and fish were recorded with natural or anthropogenic modifications in a sequence of 11000 years (Late Pleistocene–late Holocene). The largest proportion of the sample including rodents, didelphid marsupials, birds, frogs and some fish has traces of gastric digestion and skeletal proportions that suggests that it was deposited by nocturnal prey birds. These accumulations of bones have very homogeneous alterations throughout the stratigraphic sequence. The accumulation of snakes would have occurred by circumstantial death on the cave. The skeletal remains of cavid rodents, from the latest Holocene, have cut marks of artifacts and a skeletal preservation which demonstrate its anthropogenic manipulation. The most frequent alterations were post-depositional breakage. Roots marks and mineral deposits presented increasing or decreasing trends in its frequencies in the sequence.
KEY WORDS. Bone modifications. Owl pellets. Skeletal preservation.

Like other bird species, Eagle Owls take baths in ashes and sand in order to cleanse their skin and
plumage. It has now been discovered that, at two breeding sites in south-eastern Bulgaria, Eagle Owls
also use the ashes of burnt car tyres for this purpose. The toxic substances in this ash could have negative
effects on the owls from these breeding sites. This does not however represent a general threat to the
Eagle Owl population, as locations where tyres are burnt illegally are uncommon in Bulgaria. In some
developing countries however, where burning of car tyres occurs more frequently, this could prove to be
dangerous for dust-bathing birds.

- by Boyan Milchev
- •
- Owl ecology, Raptors and owls
- by Collins O'hawa
- •
- Owl ecology

Fragmentation of native forest and woodland by clearing for agriculture and urban developments has had a greater effect than logging on large forest owls and their arboreal marsupial prey. In this study, assessments were made of the contribution of forest and woodland fragments on privately-owned and unprotected lands towards the regional conservation of these species in southeastern New South Wales.
Methods: A total of 120 sites was located evenly throughout the privately-owned or otherwise unprotected lands, including vacant crown land and leasehold land, in southeastern New South Wales. Sites were located on public roads in or near fragments of native forest or woodland. Each site was classified subjectively by the degree of fragmentation in the landscape. A habitat fragmentation score ranging from 1-6 was estimated within a circle of 1 km radius (314 ha) around each site. The classification was based on the assumption that at least some cleared land was present in the landscape surrounding each site.
Results: Small (<200 ha) fragments did not provide a significant reservoir for populations of the Powerful Owl (Ninox strenua), Sooty Owl (Tyto tenebricosa) and Masked Owl (T. novaehollandiae). Virtually all records of these owls in the region were associated with extensively forested areas or occurred within 1 km of the boundary of these areas (mainly state forests, national parks and nature reserves).
Important owl prey, in particular the Common Ringtail Possum (Pseudocheirus peregrinus), Greater Glider (Petauroides volans), Yellow- bellied Glider (Petaurus australis) and the Sugar Glider (Petaurus breviceps), were either absent or less abundant in small forest fragments. The Barn Owl (Tyto alba), a non- forest species, and two other nocturnal “forest” birds, the Southern Boobook (Ninox novaeseelandiae) and Australian Owlet- nightjar (Aegotheles cristatus), were surprisingly common in small forest and woodland fragments.

- by Matthew Stanton
- •
- Zoology, Conservation Biology, Conservation, Wildlife Biology

- by Ricardo Figueroa
- •
- Conservation Biology, Life history, Ecology, Animal Behaviour

The Roach's mouse-tailed dormice (Myomimus roach!) is an endangered mammal in Europe with poorly known distribution and biology in Bulgaria. Cranial remains of 15 specimens were determined among 30532 mammals in Barn Owl (Tyto alba) pellets in 35 localities from 2000 to 2008 and 32941 mammals in Eagle Owl (Bubo bubo) pellets in 59 localities from 1988 to 2011 in SE Bulgaria. This dormouse was present with single specimens in 11 localities and whit 4 specimens in one locality. It is one of the rarest mammals in the region that forms only up to 1% by number of mammalian prey in the more numerous pellet samples. The existing protected areas ecological network covers six out of 15 (40%) localities where the species has been detected in the last two decades. We discuss the necessity of designation of new Natura 2000 zones for the protection of the Roach's mouse-tailed dormouse in Bulgaria.

- by Valeri Georgiev
- •
- Conservation, Biology, Mammalogy, DISTRIBUTION
- by Piero Ramirez
- •
- Zoology, Conservation Biology, Ecology, Animal Behaviour
- by Crizanto Brito de Carvalho and +2
- •
- Birds, OWL, Owl ecology, Raptors and owls