Migrating birds drawn away from rural areas by lights

STREET lights are disorienting migrating birds and causing them to divert to urban gardens, a study using artificial intelligence has found.

Scientists from the British Trust for Ornithology (BTO) found that calling rates of migrating blackbirds, song thrushes and redwings were significantly higher over brightly lit towns and cities.

They believe an increasing number of birds are being attracted to areas with artificial lighting leading them to perhaps make their homes in urban gardens rather than the countryside.

Throughout the year many species of birds fly over Britain on their way to nest, or move to warmer climes.

About 80 per cent of summer migrants do so at night with up to 150million crossing the North Sea under cover of darkness during the autumn.

The study, conducted in Cambridgeshire between late September and mid-november 2019 used passive acoustic monitoring devices to capture the presence of nocturnally migrating thrushes passing over gardens from the brightly lit city of Cambridge to the darker countryside that surrounds it.

The audio recordings were then processed and analysed using the latest neural network computing approaches. The data showed that the more artificial light there was, the higher the calling rate. Detected numbers of blackbirds, were approximately five times higher in the brightest areas compared to the darkest areas. The rate of redwings was four times higher and song thrushes saw a threefold increase.

Simon Gillings, principal data scientist at the BTO, said: “There are three reasons which could act individually,

‘Evidence suggests birds are attracted by the light but their calling rates may rise as it disorientates them’

or in combination, to explain this result.

“Birds could be attracted to lit areas, so more birds are present calling than over dark areas, birds might fly at lower altitude over lit areas, so more calls are detectable, or individual birds might call more often over lit areas.

“Evidence from other studies strongly suggest that birds are attracted by the light, but it is worth noting that the calling rates of individuals may also increase as they become disoriented by the lights.”

The research was published in the journal