If you want to slash bird deaths at a stroke then turn the lights off at night in city buildings. Ornithologists and bird lovers have long criticised the domestic, stray and feral cat for decimating bird numbers across the planet. They lobby governments to do all manner of things to stop this happening, some of which are cruel to cats. Here is a humane, human-focused, strategy which is very simple to operate and which can cut bird deaths during the spring migration by a sixth of previous levels. And it might reduce bird death by up to one eleventh of previous deaths in the autumn.
These are the findings of a study published in Proceedings of the National Academy of Sciences. David Willard of the Chicago Field Museum has said that over 43 years, 40,000 birds have been killed by the museum situated on the city’s Lake Michigan shore after hitting the glass frontage of the conference centre. He discovered that the fewer number of lights that are left burning overnight the fewer the number of birds that crash into the conference centre and are killed. As you can see the differences are great.
Overall, the data shows a fall from an average of 855 spring deaths to 228. And the effect is immediate and positive. Perhaps the interesting part of this research, other than the great good news that it is to bird lovers and ornithologists, is that they don’t know why birds stop flying into buildings with the lights off.
It appears that the lights in mainly tall, glass-fronted city buildings confuse birds’ navigation systems when flying during nocturnal migrations. Perhaps they use the light of the stars or the moon and incorporate this skill into their ability to detect the earth’s magnetic field. They are clearly disorientated because they cannot detect that they are flying into a building albeit it is glass and therefore transparent.
It is not unusual for large office blocks and downtown skyscrapers et cetera to leave their lights on at night. They appear to do this for three reasons: office cleaning, building security and safety to stop aircraft flying into the building. The downside is that it kills birds.
Perhaps a compromise is in order because you can’t expect management to stop cleaning offices and slacken off security measures. The only compromise that I can think of immediately is to fix black out blinds to the windows. The same sort of blinds that homeowners used to try and help their baby get a good night’s sleep.
I would hope that the bird lobby latch onto this study and start pressurising big business into doing something like this. It is suggested in the study that turning off office block lights would slash the annual toll of building collisions which is responsible for an estimated 300 million to 1 billion bird deaths in the US alone.
I have located the study on the Internet. They say that the “magnitude of nocturnal bird migration, building light output, and wind conditions are the most important predictors of fatal collisions.”
As for the wind conditions this applies to the Chicago lakeshore when the winds concentrate birds along this area. If the “lighted window area” is decreased by 50% it decreases collision counts by a factor of 11 in spring and a factor of 6 in autumn (fall). And they expect a reduction in bird mortality of about 60% at the conference centre mentioned above by decreasing the lighted window area to the minimum amount based upon past records. They believe that their findings have global implications although their research concerned a single building in a particular place.
P.S. Are you surprised like me why you never see thousands of birds littering the pavement around large buildings in the morning? Judging by this study there should be hundreds of them at least. It must mean that scavengers such as foxes and indeed stray and feral cats are devouring these carcasses. And if cats are doing it then they are doing the city a favour, perhaps.
I am indebted to The Times newspaper for this story.
SOME MORE ON BIRDS IN RELATION TO CATS:
POLL: how many birds does your cat kill per year? Please complete it to scotch ‘rumours’ of cats killing billions of birds.