Method to improve the survival of night-swarming mayflies near bridges in areas of distracting light pollution

Numerous negative ecological effects of urban lighting have been identified during the last decades. In spite of the development of lighting technologies, the detrimental effect of this form of light pollution has not declined. Several insect species are affected including the night-swarming mayflyEphoron virgo: when encountering bridges during their mass swarming, these mayflies often fall victim to artificial lighting. We show a simple method for the conservation of these mayflies exploiting their positive phototaxis. With downstream-facing light-emitting diode beacon lights above two tributaries of the river Danube, we managed to guide egg-laying females to the water and prevent them from perishing outside the river near urban lights. By means of measuring the mayfly outflow from the river as a function of time and the on/off state of the beacons, we showed that the number of mayflies exiting the river's area was practically zero when our beacons were operating. Tributaries could be the sources of mayfly recolonization in case of water quality degradation of large rivers. The protection of mayfly populations in small rivers and safeguarding their aggregation and oviposition sites is therefore important.</jats:p

Light Pollution Survey in Hungarian National Parks = Fényszennyezés felmérés a nemzeti parkokban

We have started a light pollution survey in the Hungarian national parks. We use a mobile laboratory consisting of digital cameras and robotic panorama heads to gather high-resolution panorama imaging radiometry. The same type of cameras with fish-eye lenses are used in fix monitoring stations. Parallel to the imaging radiometry, we measure the spectral distribution of the sky radiation. The spectroradiometry provides additional calibration check on the measurements and further information on the sources of light. The mobile laboratory provides an excellent spatial resolution at a given national park while the monitoring all-sky camera stations add the possibility to detect temporal changes in night sky quality. We developed new SI traceable metrics for the measurement of night sky quality. The RGB colour channels of the camera provide an optimal way to obtain multispectral radiance information. The selected metric is the band-averaged spectral radiance. Besides, we use a colour enhancement technique to find traces of different sources of night sky radiance. In the near future, we expect a large amount of high-quality data from the Hungarian national parks, which provide an outstanding possibility in light pollution related and atmospheric research. In the paper, we present the first results of the sky quality survey. ----- FÉNYSZENNYEZÉS FELMÉRÉS A NEMZETI PARKOKBAN Fényszennyezés-felmérést kezdtünk a magyarországi nemzeti parkokban. A vizsgálathoz digitális kamerákból és automata panorámafejekből álló hordozható laboratóriumot használunk, amellyel lehetőség van a nagy felbontású panorámaleképező radiometria végzésére. Ugyanilyen típusú kamerákat és halszemoptikákat állandó telepítésű mérőállomásokon is használunk. A leképező radiometriával párhuzamosan az égbolt fénylésének spektrális eloszlását is mérjük. A spektroradiometria járulékos kalibrációs információt szolgáltat a mérésekhez, ezen kívül segít a lehetséges források megkülönböztetésében is. A hordozható laboratórium megfelelő térbeli felbontást szolgáltat a nemzeti parkokban, míg az állandó teljeségbolt-mérőállomások biztosítják azt az időbeli felbontást, amellyel az égboltminőség változásait érzékelhetjük. Kidolgoztunk egy SI-egységekre visszavezethető metrikát az égboltminőség méréséhez, a kiválasztott metrika a sávátlagolt spektrális sugársűrűség. Ezen kívül egy színkiemeléses eljárást is alkalmazunk, amellyel az égbolt fénylésének különböző forrásainak a jeleit detektálhatjuk. A közeljövőben a magyarországi nemzeti parkokból nagy mennyiségű, jó minőségű adatra számíthatunk, ami kiváló lehetőséget ad a fényszennyezéssel kapcsolatos és légkörfizikai jellegű kutatá- sokhoz. A jelen cikkben bemutatjuk az égboltminőség-felmérés első eredményeit

Light Pollution Survey in Hungarian National Parks

We have started a light pollution survey in the Hungarian national parks. We use a mobile laboratory consisting of digital cameras and robotic panorama heads to gather high-resolution panorama imaging radiometry. The same type of cameras with fish-eye lenses are used in fix monitoring stations. Parallel to the imaging radiometry, we measure the spectral distribution of the sky radiation. The spectroradiometry provides additional calibration check on the measurements and further information on the sources of light. The mobile laboratory provides an excellent spatial resolution at a given national park while the monitoring all-sky camera stations add the possibility to detect temporal changes in night sky quality. We developed new SI traceable metrics for the measurement of night sky quality. The RGB colour channels of the camera provide an optimal way to obtain multispectral radiance information. The selected metric is the band-averaged spectral radiance. Besides, we use a colour enhancement technique to find traces of different sources of night sky radiance. In the near future, we expect a large amount of high-quality data from the Hungarian national parks, which provide an outstanding possibility in light pollution related and atmospheric research. In the paper, we present the first results of the sky quality survey. ----- FÉNYSZENNYEZÉS FELMÉRÉS A NEMZETI PARKOKBAN Fényszennyezés-felmérést kezdtünk a magyarországi nemzeti parkokban. A vizsgálathoz digitális kamerákból és automata panorámafejekből álló hordozható laboratóriumot használunk, amellyel lehetőség van a nagy felbontású panorámaleképező radiometria végzésére. Ugyanilyen típusú kamerákat és halszemoptikákat állandó telepítésű mérőállomásokon is használunk. A leképező radiometriával párhuzamosan az égbolt fénylésének spektrális eloszlását is mérjük. A spektroradiometria járulékos kalibrációs információt szolgáltat a mérésekhez, ezen kívül segít a lehetséges források megkülönböztetésében is. A hordozható laboratórium megfelelő térbeli felbontást szolgáltat a nemzeti parkokban, míg az állandó teljeségbolt-mérőállomások biztosítják azt az időbeli felbontást, amellyel az égboltminőség változásait érzékelhetjük. Kidolgoztunk egy SI-egységekre visszavezethető metrikát az égboltminőség méréséhez, a kiválasztott metrika a sávátlagolt spektrális sugársűrűség. Ezen kívül egy színkiemeléses eljárást is alkalmazunk, amellyel az égbolt fénylésének különböző forrásainak a jeleit detektálhatjuk. A közeljövőben a magyarországi nemzeti parkokból nagy mennyiségű, jó minőségű adatra számíthatunk, ami kiváló lehetőséget ad a fényszennyezéssel kapcsolatos és légkörfizikai jellegű kutatá- sokhoz. A jelen cikkben bemutatjuk az égboltminőség-felmérés első eredményeit

North error estimation based on solar elevation errors in the third step of sky-polarimetric Viking navigation.

The theory of sky-polarimetric Viking navigation has been widely accepted for decades without any information about the accuracy of this method. Previously, we have measured the accuracy of the first and second steps of this navigation method in psychophysical laboratory and planetarium experiments. Now, we have tested the accuracy of the third step in a planetarium experiment, assuming that the first and second steps are errorless. Using the fists of their outstretched arms, 10 test persons had to estimate the elevation angles (measured in numbers of fists and fingers) of black dots (representing the position of the occluded Sun) projected onto the planetarium dome. The test persons performed 2400 elevation estimations, 48% of which were more accurate than ±1°. We selected three test persons with the (i) largest and (ii) smallest elevation errors and (iii) highest standard deviation of the elevation error. From the errors of these three persons, we calculated their error function, from which the North errors (the angles with which they deviated from the geographical North) were determined for summer solstice and spring equinox, two specific dates of the Viking sailing period. The range of possible North errors Δω(N) was the lowest and highest at low and high solar elevations, respectively. At high elevations, the maximal Δω(N) was 35.6° and 73.7° at summer solstice and 23.8° and 43.9° at spring equinox for the best and worst test person (navigator), respectively. Thus, the best navigator was twice as good as the worst one. At solstice and equinox, high elevations occur the most frequently during the day, thus high North errors could occur more frequently than expected before. According to our findings, the ideal periods for sky-polarimetric Viking navigation are immediately after sunrise and before sunset, because the North errors are the lowest at low solar elevations

Stripes disrupt odour attractiveness to biting horseflies : Battle between ammonia, CO2, and colour pattern for dominance in the sensory systems of host-seeking tabanids

As with mosquitoes, female tabanid flies search for mammalian hosts by visual and olfactory cues, because they require a blood meal before being able to produce and lay eggs. Polarotactic tabanid flies find striped or spotted patterns with intensity and/or polarisation modulation visually less attractive than homogeneous white, brown or black targets. Thus, this reduced optical attractiveness to tabanids can be one of the functions of striped or spotty coat patterns in ungulates. Ungulates emit CO2 via their breath, while ammonia originates from their decaying urine. As host-seeking female tabanids are strongly attracted to CO2 and ammonia, the question arises whether the poor visual attractiveness of stripes and spots to tabanids is or is not overcome by olfactory attractiveness. To answer this question we performed two field experiments in which the attractiveness to tabanid flies of homogeneous white, black and black-and-white striped three-dimensional targets (spheres and cylinders) and horse models provided with CO2 and ammonia was studied. Since tabanids are positively polarotactic, i.e. attracted to strongly and linearly polarised light, we measured the reflection–polarisation patterns of the test surfaces and demonstrated that these patterns were practically the same as those of real horses and zebras. We show here that striped targets are significantly less attractive to host-seeking female tabanids than homogeneous white or black targets, even when they emit tabanid-luring CO2 and ammonia. Although CO2 and ammonia increased the number of attracted tabanids, these chemicals did not overcome the weak visual attractiveness of stripes to host-seeking female tabanids. This result demonstrates the visual protection of striped coat patterns against attacks from blood-sucking dipterans, such as horseflies, known to transmit lethal diseases to ungulates