Night lights cause severe loss of sleep for pigeons and magpies

City lights could have a serious impact on the sleep patterns of birds, according to the first study to look at neurological activity in animals thought to be affected by light pollution.

Researchers used miniature sensors to record brain activity in pigeons and magpies on three nights in an indoor aviary. On the second night, the birds were exposed to lights with a similar intensity to street lights. The study looked at both white light and amber light, the latter of which may have less of an effect on sleep patterns, previous research has suggested.

Both rapid eye movement (REM) sleep and non-REM sleep were affected by the lighting. Magpies were more affected by white light than amber light, losing 76 per cent of their non-REM sleep, while pigeons lost about 4 hours of sleep in total, regardless of the type of light.

In the wild, birds might choose to avoid sleeping under lights, but some wild pigeons and magpies have been found to sleep in conditions like those in the study, says Farley Connelly at the University of Melbourne and La Trobe University, Australia, who co-authored the study. “We have even seen pigeons roosting directly opposite bright white security lights,” he says.

The consequences of disturbed sleep for the birds will depend on whether they can get used to light at night, says co-author Anne Aulsebrook, also at the University of Melbourne and La Trobe University. “Sleep loss can cause problems for behaviour, health and development, so if birds can’t adapt or tolerate light at night, they might suffer poorer health, produce fewer offspring or have to find new habitats,” she says.