The increasing use of nest box cameras has shown how frequently garden nest boxes are used by blue tits for winter roosting.
Research has shown that, to keep warm, a blue tit can burn up more than 5% of its bodyweight in a single cold night. It looks for a secure, sheltered place to roost and will often return to that season’s nest site. When the weather is particularly harsh, blue tits will roost with other family members, all squeezed together to reduce heat loss.
To help your garden’s blue tits through the winter, you can turn your nesting box into a roosting box quite easily.
- Take down the box and remove the nest from the box, including any unhatched eggs. Remember: it’s only legal to do this between August and January.
- Clean the box thoroughly; a kettleful of boiling water will deal with parasites and their eggs. Make sure the box is fully dry.
- Put in natural insulating materials: wool, dried grasses from your garden, dried moss.
- Some people turn the box upside down and fix the lid shut; this puts the entrance hole near the bottom of the box and prevents the heat rising from the roosting birds from escaping.
Here is a time-lapse video of a single blue tit roosting in an empty nest box, squashing itself into a corner, puffing its feathers up and tucking its head under its wing to manage heat-loss. This box has been cleaned out but in the wild, a blue tit roosting in an old nest hole would have had the remains of the nest, moss, animal hair and feathers, to protect itself against the cold.
A handful of insulating material might have made the cold night easier for this tiny bird.