I’m afraid that homeowners who like garden lights need to consider others. The lights are disrupting birds’ sleep. A study by the University of Melbourne in conjunction with La Trobe University (Melbourne) published in Current Biology is apparently the first to measure this aspect of wild animal behaviour.
Just like humans, sleep is important for animals to enable them to thrive. The lead author of the study, Dr Anne Aulsebrook, said that, “…Our findings suggest the relative impacts of light pollution on birds may be specific-specific [specific lighting affecting specific bird species]. Amber lighting can reduce the disruption in some birds but it is not a solution for all species.”
Clearly white light tends to have a more damaging impact on birds. The study observed the effect of garden lights on magpies and pigeons. The study found that they “toss and turn” trying to get to sleep like humans.
Disrupted sleep in birds means that they have to catch up in the daytime which in turn means that they are more vulnerable to predators and have less time to forage for food. They also have less time to search for mates.
Garden lights which are comparable in intensity the street lighting can disrupt their sleep regardless of the colour of the light.
They discovered that different bird species have different reactions to night-time light. For example, magpie sleep was more disrupted under white light compared to amber light while both amber and white light disrupted the steep of pigeons.
Neither bird species fully recovered lost sleep by daytime snoozing. Further research into avian circadian rhythms needed to be carried out they suggested.
The recommendations are to switch off porch lights, install sensor lights, remove decorative lights on trees, balconies and other outdoor structures. Parking lights and street lights should be directed to the ground or shielded.
Comment: it is an interesting study because you can be certain that nobody has thought about the impact that garden lights or light surrounding gardens have on the sleep of birds. It is another illustration of the impact on wildlife by human activity which is so extensive that it has resulted in what is described as the sixth mass extinction of wild species on the planet.