Animal world Too much light at night disturbs great tits when breeding
Great tits spend less time on their eggs in urban nesting boxes due to light pollution. (theme picture)
Image: Keystone
Brightly lit cities at night (pictured: Zurich) discourage great tits from breeding in their nest boxes. (theme picture)
Image: Keystone
Great tits spend less time on their eggs in urban nesting boxes due to light pollution. (theme picture)
Image: Keystone
Brightly lit cities at night (pictured: Zurich) discourage great tits from breeding in their nest boxes. (theme picture)
Image: Keystone
Great tits have fewer young in nesting boxes in the city than in forests. According to a new study, the reason for this is light pollution. Great tits are more restless at night in the city and warm their eggs less.
25.03.2025, 10:13
SDA
In order to investigate the influence of humans on breeding birds, a new study involving the Sempach Ornithological Institute compared the hatching rate of great tits nesting in forests with those in the city. According to a press release issued by the ornithological station on Tuesday, the results are clear: more young hatch when the great tits constantly warm their eggs during the night.
However, they only do this in the forest and much less in urban nesting boxes. In the city, they are all the more restless the more brightly lit the locations of their nests are. The great tits therefore warm their eggs less consistently.
The fact that even common and well-adapted birds such as the great tit have problems with nocturnal light is an alarm signal for the ornithological station. It is therefore important to preserve dark places for nocturnal and less adaptable animals such as owls and bats.
Light pollution also dulls the birds' sense of direction, especially on nights with fog and dense clouds, the press release continues. When returning from their wintering grounds, they orient themselves by the stars, among other things, which is why they depend on a starry sky on their journey.
Avoiding unnecessary light at night is therefore a top priority for the ornithological station. The environmental and nature conservation organization therefore recommends, among other things, so-called "full cut-off lights", which do not emit any light above the horizontal and thus reduce the light intensity.
