Artificial lighting disrupted the structure and duration of sleep in pigeons and crows-whistlers. To such conclusion the Australian researchers, conducted a series of experiments with these birds. The reaction to light pollution was species-specific: if the pigeons are equally difficult to sleep as the white and orange light, for Raven orange light was much less harmful. As noted by the authors in an article for the journal Current Biology, the results of the study should be taken into account, assessing how light pollution affects the environment.
Artificial light at night adversely affects sleep quality of humans and animals. Especially harmful is the short-wave part of the spectrum, which is perceived as blue light. To reduce the negative effect, the authorities of some cities to replace the white lights on the orange, the radiation of which is the proportion of shortwave light less. However, it remains unclear how such measures are useful to wildlife.
To understand this issue decided by a team of researchers headed by Ann Alsbrook (Anne E. Aulsebrook) from the University of Melbourne. They focused on two types of birds: glaucous domestic pigeons (Columba livia) and crows wild-the Whistler (Cracticus tibicen), which are often found in cities throughout Australia (because of the black and white colouring they are often called “magpie”). They were placed in outdoor aviaries and conducted a series of experiments.
First, the researchers assessed the effect of white light on sleep quality in nine pigeons. During the first night the birds were allowed to sleep in the dark, and the next turned them to the light of intensity comparable with the city lights. The third night was restorative, so that the light once again left off.
Team members compared the quality of sleep in birds is studied under different levels of illumination. It turned out that the white light made the birds more awake and reduced the duration of fast and slow sleep. The next day, the doves longer than usual slept in the afternoon, which allowed to partially compensate for these losses. However, the duration of NREM sleep, including REM deep sleep, remained shorter than usual even during the first recovery night. Only the second night after the experiment, the pigeons sleep patterns returned to normal.
To find out how the birds affected by the orange light, the experiment was repeated in slightly modified form. Once again, scientists tracked the sleeping patterns of pigeons (at this time eight individuals) for three nights, but half of the birds included white lighting, and half — orange. After 4-6 days of birds from the two groups are reversed: those who are in the first phase were exposed to white light, turned orange, and Vice versa. As in the first experiment, the white light of the serious disruption to the sleep patterns of pigeons. The influence of the orange light was just as strong.
At the last stage of exposure to artificial light was subjected to eight crows-whistlers. The Protocol of the experiment was almost the same as in the first experiment, however, the light birds are included only for four hours during the night. Half of the individuals were influenced by white light, and half — orange. 48 hours after at night they changed places and repeated the experience.
Like pigeons, crows-whistlers white light greatly disrupted the structure of sleep. However orange illumination has had on these birds much smaller impact. Although both types of lights has reduced the duration of REM sleep from the Raven, the orange is not so strongly influenced the phase of slow sleep, as well as the overall intensity of sleep. He also, to a lesser extent contributed to the revivals at night.
The results of the experiment indicate that the response to color of night lighting may vary considerably from species to species. This may be due to peculiarities of their ecology or sensitivity. This aspect should be considered when assessing the impact of city lights on the environment. In this case, the authors were able to confirm that at least for certain species of birds replace the white lights on the orange may be favorable.
Light pollution is not the only problem faced by urban birds. As found by Hungarian scientists, great Tits (Parus major) in urban areas is much more difficult to raise offspring than their forest brethren. It’s the lack of insects required for feeding the Chicks.
Sergey Knee High