Where do birds go at night? University study is providing answers

Cutting-edge research by University of Gloucestershire is uncovering the night-time secrets of some of the UK’s most familiar garden birds and providing important data to help address their alarming decline in numbers.

Where woodland birds sleep at night during the winter remains one of the last great mysteries of the animal kingdom. These tiny birds have to survive up to 16 hours of darkness and cold when they are unable to feed, and choosing a good sleeping site is crucial to their surviving four long winter months.

University wildlife experts joined forces with the Gloucestershire Naturalists Society in the first study of its kind using Very High Frequency (VHF) radio tracking to discover where birds choose to sleep or settle to rest at night (roost) during the winter, after foraging during the day.

The research team, including six students from the University’s MSc Applied Ecology programme, employed tracking methods in three locations in Gloucestershire to record the winter night-time roosting habits of four popular woodland species – the European robin, Eurasian blackbird, great tit and dunnock.

The results of the study – funded by the British Ecological Society – will help to inform and support management practices in woodland areas to protect species, following a national assessment that showed a 37% decline in woodland birds since 1970.

The European robin – voted Britain’s favourite bird – was found on average to roost within eight metres of its roost site from the previous night (showing only small variation in roosting sites). The Eurasian blackbird, great tit and dunnock tended to roost up to 20 metres away from their previous roost location (showing large variation in roosting sites).

The study suggests that the European robin and dunnock prefer roost sites no higher than four metres above the ground, on average, but the Eurasian blackbird and great tit choose sites that were more than six metres above the ground.

In terms of places where they roost, European robins overwhelmingly favoured laurel trees. In contrast, the study found the Eurasian blackbird roosted in a range of different habitats between nights (including Sycamore, Bamboo, Bramble, Laurel and evergreen pines).

Dunnocks were found to roost in ivy-covered tree stumps, bramble, Hawthorn and a range of garden shrubs. The great tits in the study roosted in beech and sycamore, and occasionally laurel.

Differences in roosting behaviour

Dr Mark O’Connell, Senior Lecturer in Practical Ecology at the University, said: “Our findings suggest that none of the birds we were tracking flew large distances to get to their roost sites, but were using vegetation in local areas where they were located during the day.

“It was clear that there were differences between the species in roosting behaviour, particularly in relation to variation in height of the roost site and the vegetation types used.

“We look forward to carrying our further research to help inform woodland management practices, including around the relationship between habitat use and availability, and how supplementary feeding by humans might affect roosting behaviour.

“We would like to thank the Gloucestershire Naturalists Society and the British Ecological Society for their support, as well as our six Master’s students who helped with the night-time tracking.”

Main image: A robin favours Laurel trees as a place to roost, according to the University’s study (photo credit Pixabay)