These boxes were designed for roosting birds and about 5 of them were made for the garden by Scouts and placed by them at various locations. Mostly grey squirrels have taken them over. Not to worry though, as there are ample tree cavities for birds who need a warm site to roost. Other species will huddle against the trunk of a tree, particularly in conifers (not all birds will use roosting boxes or, by extension, cavities).