Two baby raccoon (Procyon lotor) in a tree, in captivity, Sandstone, Minnesota, United States of America, North America

The 2000 year old Plain of Jars, Phonsavan, Xieng Khouang (Xieng Khuang) Province, Laos

Mountain bluebird (Sialia currucoides), female exiting nest cavity, Yellowstone National Park, Wyoming, United States of America, North America

Golden-fronted Woodpecker (Melanerpes aurifrons), male at nesting cavity in palm tree, Brownsville, Rio Grande Valley, South Texas, USA

Middle spotted woodpecker (Dendrocopos medius), with food in its beak at the breeding cavity, North Rhine-Westphalia, Germany, Europe

Ferruginous Pygmy-Owl (Glaucidium brasilianum), young looking out of nesting cavity, Willacy County, Rio Grande Valley, South Texas, USA

Virginia Opossum (Didelphis virginiana), adult at night looking out of tree cavity, Raleigh, Wake County, North Carolina, USA

Tawny owl (Strix aluco), adult bird looking out of a tree cavity, Frankfurt, Hesse, Germany, Europe

Raccoon (Procyon lotor), fawn looking out of its tree hollow, Hesse, Germany, Europe

Lesser Spotted Woodpecker (Dendrocopus minor, Picoides minor), male at the nest cavity in a birch tree

Middle spotted woodpecker (Dendrocopos medius), looking out of breeding cavity, North Rhine-Westphalia, Germany, Europe

Raccoon (Procyon lotor), young and fawn looking out of their tree den, Hesse, Germany, Europe

Trunk of a Baobab (Adansonia rubrostipa), the notches dug in the trunk are used to climb on the tree, Ifaty, Province of Tulear, Madagascar

Little owl (Athena noctua) perched inside an hollow oak tree, England

Mahanoro Digging Frog (Plethodontohyla notosticta) in its tree hole with his tadpoles in Tropical Rainforest, Pangalanes Canal, Ampitabe Lake, Atsinanana Region, Madagascar

Tengmalm's Owl (Aegolius funereus) in a lodge dug in a beech tree by a black woodpecker, Massif des Bauges, France

Woman planting a citrus fruit in the ground. Planting a young yuzu.

Badger (Meles meles )Female and cub on the side of an oak tree, England

Tengmalm's owl (Aegolius funereus) emerging from a cavity in a dead tree, Finland

Weasel (Mustela nivalis) inside a tree, England

Tawny Owl in Walnut tree, Auvergne France

Tawny Owl in hollow tree, Ardennes Belgium

Badger (Meles meles) coming out from under an oak tree