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Longcore, T., Rich, C., Mineau, P., MacDonald, B., Bert, D. G., Sullivan, L. M., et al. (2012). An estimate of avian mortality at communication towers in the United States and Canada. PLoS One, 7(4), e34025.
Abstract: Avian mortality at communication towers in the continental United States and Canada is an issue of pressing conservation concern. Previous estimates of this mortality have been based on limited data and have not included Canada. We compiled a database of communication towers in the continental United States and Canada and estimated avian mortality by tower with a regression relating avian mortality to tower height. This equation was derived from 38 tower studies for which mortality data were available and corrected for sampling effort, search efficiency, and scavenging where appropriate. Although most studies document mortality at guyed towers with steady-burning lights, we accounted for lower mortality at towers without guy wires or steady-burning lights by adjusting estimates based on published studies. The resulting estimate of mortality at towers is 6.8 million birds per year in the United States and Canada. Bootstrapped subsampling indicated that the regression was robust to the choice of studies included and a comparison of multiple regression models showed that incorporating sampling, scavenging, and search efficiency adjustments improved model fit. Estimating total avian mortality is only a first step in developing an assessment of the biological significance of mortality at communication towers for individual species or groups of species. Nevertheless, our estimate can be used to evaluate this source of mortality, develop subsequent per-species mortality estimates, and motivate policy action.
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Malek, I., & Haim, A. (2019). Bright artificial light-at-night is associated with increased body mass, poor reproductive success, and compromised disease tolerance in Australian budgerigars (Melopsittacus undulatus). Integr Zool, 14(6), 589–603.
Abstract: Artificial light-at-night (ALAN) can cause circadian disruption and result in adverse behavioral and ecological effects in free-living birds, but studies on captive pet birds as companion animals have been infrequent. We studied the effects of exposure to bright ALAN on body mass, melatonin sulfate levels, reproduction, and disease severity in Australian budgerigars (Melopsittacus undulatus) kept in captivity. During the experiment, birds were kept under outdoor temperature, humidity, and natural photoperiod from September to December. 48 birds were equally split into four groups (6 mating pairs each) and concurrently exposed to ALAN of 200 lux with different duration (0, 30, 60, and 90 min). Monthly observations were recorded for all dependent parameters. ALAN exposure increased mass gain and suppressed melatonin levels in a dose-dependent manner, especially during December. In addition, ALAN exposure in all duration groups decreased egg production and reduced hatchability from 61+/-14% in the ALAN-unexposed control group to 0% in the ALAN-exposed birds. Disease severity was also found to increase in line with the duration of ALAN exposure. In captive M. undulatus, ALAN exposure was demonstrated to affect photoperiodic regulation with subsequent excess mass gain, reproduction impairment, and increased susceptibility to infections plausibly through duration dose-dependent suppression of melatonin. To the best of our knowledge, this is the first study to demonstrate a possible association between acute bright ALAN of increasing duration and both natural development of infections as well as reproductive cessation in captive birds. Our findings could be used to improve breeding conditions of captive birds.
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Miller, M. W. (2006). Apparent Effects of Light Pollution on Singing Behavior of American Robins. Condor, 108(1), 130.
Abstract: Astronomers consider light pollution to be a growing problem, however few studies have addressed potential effects of light pollution on wildlife. Sunlight is believed to initiate song in many bird species. If light initiates song, then light pollution may be influencing avian song behavior at a population level. This hypothesis predicts that birds breeding in areas with large amounts of artificial light will begin singing earlier in the day than birds in areas with little artificial light. Birds in highly illuminated areas might begin singing earlier than did birds in those same areas in previous years when artificial light levels were known to be, or were presumably, lower. Also, birds should begin singing earlier within a site on brightly lit nights. In 2002 and 2003 I documented initiation of morning song by breeding American Robins (Turdus migratorius) in areas with differing intensity of artificial nocturnal light. I compared my observations among sites and against historical studies. Robin populations in areas with large amounts of artificial light frequently began their morning chorus during true night. Chorus initiation time, relative to civil twilight, was positively correlated with amount of artificial light present during true night. Robin choruses in areas with little, or presumably little, artificial light have almost never begun during true night, instead appearing to track the onset of civil twilight. Proliferation of artificial nocturnal light may be strongly affecting singing behavior of American Robins at a population level.
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Moaraf, S., Heiblum, R., Vistoropsky, Y., Okuliarova, M., Zeman, M., & Barnea, A. (2020). Artificial Light at Night Increases Recruitment of New Neurons and Differentially Affects Various Brain Regions in Female Zebra Finches. Int J Mol Sci, 21(17).
Abstract: Despite growing evidence that demonstrate adverse effects of artificial light at night (ALAN) on many species, relatively little is known regarding its effects on brain plasticity in birds. We recently showed that although ALAN increases cell proliferation in brains of birds, neuronal densities in two brain regions decreased, indicating neuronal death, which might be due to mortality of newly produced neurons or of existing ones. Therefore, in the present study we studied the effect of long-term ALAN on the recruitment of newborn neurons into their target regions in the brain. Accordingly, we exposed zebra finches (Taeniopygia guttata) to 5 lux ALAN, and analysed new neuronal recruitment and total neuronal densities in several brain regions. We found that ALAN increased neuronal recruitment, possibly as a compensatory response to ALAN-induced neuronal death, and/or due to increased nocturnal locomotor activity caused by sleep disruption. Moreover, ALAN also had a differential temporal effect on neuronal densities, because hippocampus was more sensitive to ALAN and its neuronal densities were more affected than in other brain regions. Nocturnal melatonin levels under ALAN were significantly lower compared to controls, indicating that very low ALAN intensities suppress melatonin not only in nocturnal, but also in diurnal species.
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Navarro, J. Y., & Lahti, D. C. (2014). Light Dulls and Darkens Bird Eggs. PloS one, 9(12), e116112.
Abstract: Although egg color is generally consistent within individual birds and robust to environmental variation, recent evidence suggests a degree of susceptibility to environmental perturbation or modulation of egg color. Most of this variation manifests via the physiology of the laying female, but some direct impacts of the environment on laid eggs have also been discovered. Here we test whether light changes bird egg color and we quantify its effect, by subjecting variable blue-green eggs of Rüppell's weaver (Ploceus galbula) to a broad-spectrum light source under laboratory conditions, and measuring egg reflectance every few hours. Eggshells gradually decreased in reflectance across the entire measured wavelength spectrum of 250–800 nm. Reflectance peaks were disproportionately affected, such that the height decreased of both the blue-green peak and the smaller UV peak typical of blue-green eggs. The reflectance of lighter eggs was affected slightly more than that of darker eggs. These changes are similar to previous results for changes over long periods of time in darkness, suggesting that light might hasten the same process of pigment degradation that proceeds even without light. Comparison between the experimental light source and both sunlight and typical artificial lighting situations raises the possibility that significant color change might occur during incubation in some birds, but indicates that eggshell illumination in museums for short periods of study is unlikely to affect their color to a detectable extent. Additional research should be performed on eggs of other species and in other light environments, with an eye to an eventual generalized model of the effect of light on eggshell color.
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