Skylight Polarization Patterns and the Orientation of Migratory Birds

1989 ◽  
Vol 141 (1) ◽  
pp. 241-256
Author(s):  
KENNETH P. ABLE
Keyword(s):  
Migratory Birds ◽  
Polarized Light ◽  
Degree Of Polarization ◽  
Zonotrichia Albicollis ◽  
Directional Information ◽  
Clear Sky ◽  
Migratory Orientation ◽  
Skylight Polarization ◽  
Colour Patterns ◽  
Artificial Nature

Patterns of polarized light present in the clear dusk sky provide directional information relevant to the orientation behaviour of migratory birds. Experiments performed with white-throated sparrows (Zonotrichia albicollis) and American tree sparrows (Spizella arborea), North American night migrants, examined migratory orientation between the time of sunset and the first appearance of stars under several manipulations of skylight polarization patterns. Under clear skies, birds tested in Emlen funnel orientation cages oriented their hopping basically parallel to the E-vector of polarized light, with a bias towards the brightest part of the sky (sunset direction). Under solid, thick overcast conditions (no polarized light from the natural sky), birds showed axially bimodal hopping orientation parallel to an imposed E-vector. When birds were tested in cages covered with depolarizing material under a clear sky, their hopping orientation was seasonally appropriate and indistinguishable from controls viewing an unaltered clear sky. Skylight polarization patterns are not necessary for the occurrence of migratory orientation, but birds respond strongly to manipulations of the E-vector direction. The results reported here support the hypothesis that the relevant stimulus is the E-vector orientation rather than other parameters of skylight, e.g. intensity or colour patterns, degree of polarization. It appears that these night migrants are using skylight polarization at dusk as one of a set of multiple compass capabilities. Because of the necessarily artificial nature of the polarized light stimuli used in the experimental manipulations, it has not been possible to establish the relationship between this orientation cue and other known mechanisms (magnetic, sun and star compasses).

Magnetic orientation of snow buntings (Plectrophenax nivalis), a species breeding in the high Arctic: passage migration through temperate-zone areas

1996 ◽  
Vol 199 (9) ◽  
pp. 1899-1905
Author(s):  
R Sandberg ◽  
J Pettersson
Keyword(s):  
Magnetic Fields ◽  
High Arctic ◽  
Temperate Zone ◽  
Axial Orientation ◽  
Magnetic Orientation ◽  
Directional Information ◽  
Clear Sky ◽  
Migratory Orientation ◽  
Plectrophenax Nivalis ◽  
Auxiliary Source

Orientation tests were conducted with snow buntings (Plectrophenax nivalis) exposed to artificially manipulated magnetic fields, during both spring and autumn migration. Experiments were run under clear sunset skies and under simulated complete overcast. The birds closely followed experimental shifts of the magnetic fields during both seasons regardless of whether they had access to celestial cues. Clear-sky tests in vertical magnetic fields resulted in a significant bimodal orientation, the directionality of which was almost identical during spring and autumn. When the snow buntings were deprived of celestial directional information and tested in vertical magnetic fields, they failed to show any statistically significant mean directions in either spring or autumn. The results demonstrate that snow buntings possess a magnetic compass and suggest that magnetic cues are of primary importance for their migratory orientation while on passage through temperate-zone areas. However, the axial orientation in vertical magnetic fields under clear skies may indicate an involvement of celestial cues as an auxiliary source of directional information.

scholarly journals Skylight Polarization patterns and Animal Orientation

1982 ◽  
Vol 96 (1) ◽  
pp. 69-91 ◽  
Author(s):  
MICHAEL L. BRINES ◽  
JAMES L. GOULD
Keyword(s):  
Rayleigh Scattering ◽  
Polarized Light ◽  
Processing System ◽  
Light Polarization ◽  
Degree Of Polarization ◽  
Atmospheric Conditions ◽  
Apparent Paradox ◽  
Skylight Polarization ◽  
Visible Wavelengths ◽  
Vector Orientation

1. Although many invertebrate animals orient by means of ultraviolet sky-light polarization patterns, existing measurements of these patterns are inadequate for full analysis of the biologically relevant information available from the sky. To fill this gap we have used a precision scanning polarimeter to measure simultaneously the intensity, degree, and direction of vibration (E-vector orientation) of polarized light at 5° intervals over the sky. The resulting sky maps were constructed for u.v. (350 nm) and visible wavelengths (500 and 650 nm) under a variety of atmospheric conditions. 2. Our measurements confirmed that the patterns of radiance and degree of polarization of skylight are highly variable and hence unreliable as orientation cues; but patterns of E-vector orientation are relatively stable and predictable over most of the sky under all but very hazy or overcast conditions. 3. The observed E-vector patterns correspond more closely to predictions based on first order (Rayleigh) scattering at 650 and 500 nm than at 350 nm. This is true both in terms of absolute accuracy and the proportion of the sky with relatively ‘correct’ information. Yet most insects respond to polarization patterns only at u.v. wavelengths. This apparent paradox can perhaps be resolved by assuming that there is no great selective advantage for any particular wavelength when large areas of blue sky are visible, but that under special and difficult conditions ultraviolet has advantages over longer wavelengths. Measurements under partially cloud-covered sky, for instance, or under extensive vegetation, show that both spuriously polarized and unpolarized light resulting from reflexions present more troublesome interference at longer wavelengths than in the u.v. 4. The accuracy of orientation achieved by dancing honey bees appears to be greater than can readily be accounted for by assuming that they use a strictly geometrical or analytical processing system for their orientation to polarized light.

scholarly journals How the clear-sky angle of polarization pattern continues underneath clouds: full-sky measurements and implications for animal orientation

2001 ◽  
Vol 204 (17) ◽  
pp. 2933-2942 ◽  
Author(s):  
István Pomozi ◽  
Gábor Horváth ◽  
Rüdiger Wehner
Keyword(s):  
Single Scattering ◽  
Degree Of Polarization ◽  
Polarization Pattern ◽  
Clear Sky ◽  
Animal Navigation ◽  
Imaging Polarimetry ◽  
Polarization Compass ◽  
Sky Conditions ◽  
Perceptual Threshold ◽  
Animal Orientation

SUMMARY One of the biologically most important parameters of the cloudy sky is the proportion P of the celestial polarization pattern available for use in animal navigation. We evaluated this parameter by measuring the polarization patterns of clear and cloudy skies using 180° (full-sky) imaging polarimetry in the red (650nm), green (550nm) and blue (450nm) ranges of the spectrum under clear and partly cloudy conditions. The resulting data were compared with the corresponding celestial polarization patterns calculated using the single-scattering Rayleigh model. We show convincingly that the pattern of the angle of polarization (e-vectors) in a clear sky continues underneath clouds if regions of the clouds and parts of the airspace between the clouds and the earth surface (being shady at the position of the observer) are directly lit by the sun. The scattering and polarization of direct sunlight on the cloud particles and in the air columns underneath the clouds result in the same e-vector pattern as that present in clear sky. This phenomenon can be exploited for animal navigation if the degree of polarization is higher than the perceptual threshold of the visual system, because the angle rather than the degree of polarization is the most important optical cue used in the polarization compass. Hence, the clouds reduce the extent of sky polarization pattern that is useful for animal orientation much less than has hitherto been assumed. We further demonstrate quantitatively that the shorter the wavelength, the greater the proportion of celestial polarization that can be used by animals under cloudy-sky conditions. As has already been suggested by others, this phenomenon may solve the ultraviolet paradox of polarization vision in insects such as hymenopterans and dipterans. The present study extends previous findings by using the technique of 180° imaging polarimetry to measure and analyse celestial polarization patterns.

scholarly journals Demonstration of polarization control GaN-based micro-cavity lasers using a rigid high-contrast grating reflector

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Tsu-Chi Chang ◽  
Kuo-Bin Hong ◽  
Shuo-Yi Kuo ◽  
Tien-Chang Lu
Keyword(s):  
Semiconductor Lasers ◽  
Optical Pumping ◽  
Polarized Light ◽  
Transverse Magnetic ◽  
Bragg Reflector ◽  
Degree Of Polarization ◽  
High Contrast ◽  
Distributed Bragg Reflector ◽  
Output Mirror ◽  
High Contrast Grating

Abstract We reported on GaN microcavity (MC) lasers combined with one rigid TiO2 high-contrast grating (HCG) structure as the output mirror. The HCG structure was directly fabricated on the GaN structure without an airgap. The entire MC structure comprised a bottom dielectric distributed Bragg reflector; a GaN cavity; and a top HCG reflector, which was designed to yield high reflectance for transverse magnetic (TM)- or transverse electric (TE)-polarized light. The MC device revealed an operation threshold of approximately 0.79 MW/cm2 when pulsed optical pumping was conducted using the HCG structure at room temperature. The laser emission was TM polarized with a degree of polarization of 99.2% and had a small divergence angle of 14° (full width at half maximum). This laser operation demonstration for the GaN-based MC structure employing an HCG exhibited the advantages of HCGs in semiconductor lasers at wavelengths from green to ultraviolet.

scholarly journals Polarized proton beams from laser-induced plasmas

2019 ◽  
Vol 7 ◽  
Author(s):  
Anna Hützen ◽  
Johannes Thomas ◽  
Jürgen Böker ◽  
Ralf Engels ◽  
Ralf Gebel ◽  
...  
Keyword(s):  
Laser System ◽  
Polarized Light ◽  
Particle Beam ◽  
Degree Of Polarization ◽  
Acceleration Process ◽  
Simulation Code ◽  
Experimental Realization ◽  
Circularly Polarized Light ◽  
Spin Effects ◽  
Polarized Proton

We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the particle-in-cell (PIC) simulation code VLPL (Virtual Laser Plasma Lab) to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circularly polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms. Subsequently, their degree of polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM, Shanghai.

The use of solar cues as migratory orientation guides by the plains garter snake, Thamnophis radix

1991 ◽  
Vol 69 (10) ◽  
pp. 2700-2702 ◽  
Author(s):  
Peggy A. Lawson ◽  
Diane M. Secoy
Keyword(s):  
Polarized Light ◽  
Garter Snake ◽  
Circular Statistics ◽  
Type Ii ◽  
Garter Snakes ◽  
Type Iii ◽  
Migratory Orientation

The ability of adult plains garter snakes, Thamnophis radix, to use solar cues as orientation guides during their fall return to a communal hibernaculum in southern Canada was examined. Snakes were displaced from dens and tested in circular arenas that restricted their view of terrestrial landmarks. The results were analyzed by circular statistics. Snakes oriented along the homeward axis, indicating type II or type III orientation. A bidirectional pattern of responses suggests that polarized light may be an orientation cue.

scholarly journals Honeybee navigation: following routes using polarized-light cues

2011 ◽  
Vol 366 (1565) ◽  
pp. 703-708 ◽  
Author(s):  
P. Kraft ◽  
C. Evangelista ◽  
M. Dacke ◽  
T. Labhart ◽  
M. V. Srinivasan
Keyword(s):  
Apis Mellifera ◽  
Food Source ◽  
Polarized Light ◽  
Light Illumination ◽  
Directional Information ◽  
First Time ◽  
Behavioural Evidence ◽  
Do So

While it is generally accepted that honeybees ( Apis mellifera ) are capable of using the pattern of polarized light in the sky to navigate to a food source, there is little or no direct behavioural evidence that they actually do so. We have examined whether bees can be trained to find their way through a maze composed of four interconnected tunnels, by using directional information provided by polarized light illumination from the ceilings of the tunnels. The results show that bees can learn this task, thus demonstrating directly, and for the first time, that bees are indeed capable of using the polarized-light information in the sky as a compass to steer their way to a food source.

Optical Pumping and Optical Detection of Spin-Polarized Electrons in a Conduction Band

1971 ◽  
Vol 49 (14) ◽  
pp. 1850-1860 ◽  
Author(s):  
R. R. Parsons
Keyword(s):  
Magnetic Field ◽  
Conduction Band ◽  
Spin Polarization ◽  
Optical Pumping ◽  
Polarized Light ◽  
Degree Of Polarization ◽  
Polarized Electrons ◽  
Excitation Light ◽  
Circularly Polarized Light ◽  
Spin Polarized

Spin-polarized electrons are created in the conduction band of p-type GaSb by excitation with σ+ or σ− circularly polarized light. The degree of polarization of the photoluminescence is used to measure the optically pumped spin polarization. The measurements as a function of transverse magnetic field yield the spin-relaxation time and the lifetime of the photocreated electrons. The degree of polarization oscillates as a function of the photon energy of the excitation light. This effect is associated with mechanisms of rapid energy loss involving optical and acoustical phonons. The optical pumping is studied as a function of temperature in the range 3.5 °K ≤ T ≤ 11 °K. A maximum spin polarization [Formula: see text] is obtained at [Formula: see text]. The efficiency of the optical pumping is significantly increased with the application of a weak longitudinal magnetic field.

Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies

2007 ◽  
Vol 463 (2080) ◽  
pp. 1081-1095 ◽  
Author(s):  
Ramón Hegedüs ◽  
Susanne Åkesson ◽  
Rüdiger Wehner ◽  
Gábor Horváth
Keyword(s):  
Linear Polarization ◽  
The Sun ◽  
Direct Sunlight ◽  
Birefringent Crystal ◽  
Clear Sky ◽  
Open Sea ◽  
Skylight Polarization ◽  
Imaging Polarimetry

In sunshine, the Vikings navigated on the open sea using sundials. According to a widespread hypothesis, when the Sun was occluded by fog or clouds the Vikings might have navigated by skylight polarization detected with an enigmatic birefringent crystal (sunstone). There are two atmospheric optical prerequisites for this alleged polarimetric Viking navigation under foggy/cloudy skies: (1) the degree of linear polarization p of skylight should be high enough and (2) at a given Sun position, the pattern of the angle of polarization α of the foggy/cloudy sky should be similar to that of the clear sky. Until now, these prerequisites have not been investigated. Using full-sky imaging polarimetry, we measured the p - and α -patterns of Arctic foggy and cloudy skies when the Sun was invisible. These patterns were compared with the polarization patterns of clear Arctic skies. We show here that although prerequisite (2) is always fulfilled under both foggy and cloudy conditions, if the fog layer is illuminated by direct sunlight, prerequisite (1) is usually satisfied only for cloudy skies. In sunlit fog, the Vikings could have navigated by polarization only, if p of light from the foggy sky was sufficiently high.

scholarly journals Synaptic targets of photoreceptors specialized to detect color and skylight polarization in Drosophila

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Emil Kind ◽  
Kit D Longden ◽  
Aljoscha Nern ◽  
Arthur Zhao ◽  
Gizem Sancer ◽  
...  
Keyword(s):  
Neural Circuits ◽  
Polarized Light ◽  
Cell Types ◽  
Brain Regions ◽  
Complementary Information ◽  
Color Processing ◽  
Optic Lobes ◽  
Skylight Polarization ◽  
The World ◽  
Central Brain

Color and polarization provide complementary information about the world and are detected by specialized photoreceptors. However, the downstream neural circuits that process these distinct modalities are incompletely understood in any animal. Using electron microscopy, we have systematically reconstructed the synaptic targets of the photoreceptors specialized to detect color and skylight polarization in Drosophila, and we have used light microscopy to confirm many of our findings. We identified known and novel downstream targets that are selective for different wavelengths or polarized light, and followed their projections to other areas in the optic lobes and the central brain. Our results revealed many synapses along the photoreceptor axons between brain regions, new pathways in the optic lobes, and spatially segregated projections to central brain regions. Strikingly, photoreceptors in the polarization-sensitive dorsal rim area target fewer cell types, and lack strong connections to the lobula, a neuropil involved in color processing. Our reconstruction identifies shared wiring and modality-specific specializations for color and polarization vision, and provides a comprehensive view of the first steps of the pathways processing color and polarized light inputs.

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