Optocollic responses in adult barn owls (Tyto furcata)

AbstractBarn owls, like primates, have frontally oriented eyes, which allow for a large binocular overlap. While owls have similar binocular vision and visual-search strategies as primates, it is less clear whether reflexive visual behavior also resembles that of primates or is more similar to that of closer related, but lateral-eyed bird species. Test cases are visual responses driven by wide-field movement: the optokinetic, optocollic, and optomotor responses, mediated by eye, head and body movements, respectively. Adult primates have a so-called symmetric horizontal response: they show the same following behavior, if the stimulus, presented to one eye only, moves in the nasal-to-temporal direction or in the temporal-to-nasal direction. By contrast, lateral-eyed birds have an asymmetric response, responding better to temporal-to-nasal movement than to nasal-to-temporal movement. We show here that the horizontal optocollic response of adult barn owls is less asymmetric than that in the chicken for all velocities tested. Moreover, the response is symmetric for low velocities (< 20 deg/s), and similar to that of primates. The response becomes moderately asymmetric for middle-range velocities (20–40 deg/s). A definitive statement for the complex situation for higher velocities (> 40 deg/s) is not possible.

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Self-motion trajectories can facilitate orientation-based figure-ground segregation

Journal of Neurophysiology ◽

10.1152/jn.00439.2019 ◽

2020 ◽

Vol 123 (3) ◽

pp. 912-926

Author(s):

Arkadeb Dutta ◽

Tidhar Lev-Ari ◽

Ouriel Barzilay ◽

Rotem Mairon ◽

Alon Wolf ◽

...

Keyword(s):

Receptive Fields ◽

Visual Outcome ◽

Neural Response ◽

Head Movements ◽

Essential Property ◽

Wide Field ◽

Tyto Alba ◽

Dominant Orientation ◽

Barn Owls ◽

Detection Of Objects

Segregation of objects from the background is a basic and essential property of the visual system. We studied the neural detection of objects defined by orientation difference from background in barn owls ( Tyto alba). We presented wide-field displays of densely packed stripes with a dominant orientation. Visual objects were created by orienting a circular patch differently from the background. In head-fixed conditions, neurons in both tecto- and thalamofugal visual pathways (optic tectum and visual Wulst) were weakly responsive to these objects in their receptive fields. However, notably, in freely viewing conditions, barn owls occasionally perform peculiar side-to-side head motions (peering) when scanning the environment. In the second part of the study we thus recorded the neural response from head-fixed owls while the visual displays replicated the peering conditions; i.e., the displays (objects and backgrounds) were shifted along trajectories that induced a retinal motion identical to sampled peering motions during viewing of a static object. These conditions induced dramatic neural responses to the objects, in the very same neurons that where unresponsive to the objects in static displays. By reverting to circular motions of the display, we show that the pattern of the neural response is mostly shaped by the orientation of the background relative to motion and not the orientation of the object. Thus our findings provide evidence that peering and/or other self-motions can facilitate orientation-based figure-ground segregation through interaction with inhibition from the surround. NEW & NOTEWORTHY Animals frequently move their sensory organs and thereby create motion cues that can enhance object segregation from background. We address a special example of such active sensing, in barn owls. When scanning the environment, barn owls occasionally perform small-amplitude side-to-side head movements called peering. We show that the visual outcome of such peering movements elicit neural detection of objects that are rotated from the dominant orientation of the background scene and which are otherwise mostly undetected. These results suggest a novel role for self-motions in sensing objects that break the regular orientation of elements in the scene.

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Assessing bird collisions in the United Kingdom: Modelling frequency of bird-strike from road and rail mortality using a Bayesian hierarchical approach

10.1101/2020.12.04.412361 ◽

2020 ◽

Author(s):

Silvia Freire ◽

Lee Read ◽

Todd R. Lewis

Keyword(s):

Bird Species ◽

Early Spring ◽

Mitigation Measures ◽

Road Mortality ◽

Bayesian Hierarchical ◽

The United Kingdom ◽

Barn Owls ◽

Causes Of Mortality ◽

Sexual Bias ◽

Negative Impacts

AbstractRoads are an important way to transport people and goods, but they sometimes have negative impacts on wildlife. One of the leading causes of mortality for several species is identified as road strikes, and the most significant remains bird-vehicle collisions. This study aimed to investigate what species of birds are most affected, and what other factors impact in their susceptibility in road collisions, such as age, sex, season, and type of transports. A total of N=5413 records, and 140 bird species were documented by BTO ringers. For analysis four Bayesian Hierarchical Models were used, with random effects results showing that Barn owls were most affected by collisions. Road mortality presents the highest cause of mortality among species when contrasted with rail mortality. Age and sexual bias was detected across all species, however juveniles and males did appear to be prominent in relation to other age classes. Winter and early spring were the months with most reported casualties and 2016 had lower abundance of mortality across the 10-year period. 75% of birds were found within a week, which may indicate some bias interference from scavenging animals, as true figures could be up to 16 times more. This study discusses some mitigation measures found in current research, that could dramatically reduce numbers of birds affected each year by road mortality.

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The diet, and pellet residue taphonomy, of Barn Owls Tyto alba on a Greek island reveals an exceptional diversity of avian prey

Acrocephalus ◽

10.2478/acro-2020-0001 ◽

2020 ◽

Vol 41 (184-185) ◽

pp. 3-24

Author(s):

Anthony S. Cheke ◽

Julian P. Hume

Keyword(s):

Mus Musculus ◽

Rattus Rattus ◽

Bird Species ◽

Barn Owl ◽

Dung Beetles ◽

Tyto Alba ◽

Resident Species ◽

Barn Owls ◽

Species Proportions ◽

Greek Island

Abstract Barn Owl Tyto alba pellets and loose bones on a cave floor from Amorgos (Cyclades, Greece) were examined and the birds found to have caught at least 39 species of bird, mostly identified from humeri, plus shrews Crocidura suaveolens, a few lizards and dung beetles, in addition to their principal diet of rodents (rats Rattus rattus, mice Apodemus spp. & Mus musculus). Amongst the birds, migrants appeared most vulnerable to owl predation, with some notable exceptions, while resident species were under-represented. The range of bird species found appears to be the largest recorded for any Barn Owl study of a single site. Considerable differences were found in species proportions of taxa in fresh pellets and in loose bones, probably due to differential rates of degradation. Photographs of all humeri are included to aid identification in other studies.

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Selective gating of retinal information by arousal

10.1101/2020.03.12.989913 ◽

2020 ◽

Author(s):

Liang Liang ◽

Alex Fratzl ◽

Omar El Mansour ◽

Jasmine D.S. Reggiani ◽

Chinfei Chen ◽

...

Keyword(s):

Visual Processing ◽

Visual Information ◽

Visual Stimuli ◽

Sensory Information ◽

Visual Space ◽

Wide Field ◽

Visual Responses ◽

Visual Thalamus ◽

Spatial Frequencies ◽

Retinal Information

SummaryHow sensory information is processed by the brain can depend on behavioral state. In the visual thalamus and cortex, arousal/locomotion is associated with changes in the magnitude of responses to visual stimuli. Here, we asked whether such modulation of visual responses might already occur at an earlier stage in this visual pathway. We measured neural activity of retinal axons using wide-field and two-photon calcium imaging in awake mouse thalamus across arousal states associated with different pupil sizes. Surprisingly, visual responses to drifting gratings in retinal axonal boutons were robustly modulated by arousal level, in a manner that varied across stimulus dimensions and across functionally distinct subsets of boutons. At low and intermediate spatial frequencies, the majority of boutons were suppressed by arousal. In contrast, at high spatial frequencies, the proportions of boutons showing enhancement or suppression were more similar, particularly for boutons tuned to regions of visual space ahead of the mouse. Arousal-related modulation also varied with a bouton’s sensitivity to luminance changes and direction of motion, with greater response suppression in boutons tuned to luminance decrements vs. increments, and in boutons preferring motion along directions or axes of optic flow. Together, our results suggest that differential filtering of distinct visual information channels by arousal state occurs at very early stages of visual processing, before the information is transmitted to neurons in visual thalamus. Such early filtering may provide an efficient means of optimizing central visual processing and perception of state-relevant visual stimuli.

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Linear Visco-Resistive Computations of Magnetohydrodynamic Waves: I. The Code and Test Cases

International Astronomical Union Colloquium ◽

10.1017/s0252921100025926 ◽

1994 ◽

Vol 144 ◽

pp. 503-505

Author(s):

R. Erdélyi ◽

M. Goossens ◽

S. Poedts

Keyword(s):

Resonant Absorption ◽

Numerical Code ◽

Mhd Waves ◽

Test Cases ◽

Numerical Accuracy ◽

Element Discretization ◽

Flux Tubes ◽

Magnetohydrodynamic Waves ◽

Viscosity Coefficients ◽

Magnetic Flux Tubes

AbstractThe stationary state of resonant absorption of linear, MHD waves in cylindrical magnetic flux tubes is studied in viscous, compressible MHD with a numerical code using finite element discretization. The full viscosity tensor with the five viscosity coefficients as given by Braginskii is included in the analysis. Our computations reproduce the absorption rates obtained by Lou in scalar viscous MHD and Goossens and Poedts in resistive MHD, which guarantee the numerical accuracy of the tensorial viscous MHD code.

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STM studies of crystal growth

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086179 ◽

1991 ◽

Vol 49 ◽

pp. 374-375

Author(s):

M. G. Lagally

Keyword(s):

Crystal Growth ◽

Molecular Beam ◽

Chemical Vapor ◽

Sputter Deposition ◽

Field Of View ◽

Scanning Tunneling ◽

Wide Field ◽

Tunneling Microscopy ◽

Wide Field Of View ◽

The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

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