Bluetit hungry young nestling bird cheeping in a garden bird box, The Cotswolds, Oxfordshire, England, United Kingdom

Bluetit hungry young nestling bird awaits feeding in a garden bird box, The Cotswolds, Oxfordshire, England, United Kingdom

Bluetit bird feeding hungry young nestling in a garden bird box, The Cotswolds, Oxfordshire, England, United Kingdom

Bluetit bird feeding hungry young nestling in a garden bird box, The Cotswolds, Oxfordshire, England, United Kingdom

Newly hatched blue tit chicks and adult in a nestbox

Newly hatched blue tit chicks and adult in a nestbox

Mountain brushtail possum (Trichosurus caninus) emerging from artificial nestbox, hand-reared sub-adult male approximately 12 months old, Hopkins Creek, New South Wales, Australia, Pacific

Bird nest boxes in the Forest of Bowland, Lancashire, England, United Kingdom, Europe

Bluetit bringing food to its chicks in a nest box, England, United Kingdom, Europe

Tree Swallow, Tachycineta bicolor

Bird nesting box on a wooden telephone pole

Bird nesting box on a wooden telephone pole

Kestrel (Falco tinnunculus) perched inside a nestbox, England