Oology, , is a branch of ornithology studying bird eggs, nests and breeding behaviour. The word is derived from the Greek oion, meaning egg. Oology can also refer to the hobby of collecting wild birds' eggs, sometimes called egg collecting, birdnesting or egging, which is now illegal in many jurisdictions.
Mid-19th century illustration showing the eggs of a number of bird species
Part of the egg collection of the german Arbeitsgemeinschaft Wanderfalkenschutz (Working Group for the Protection of Peregrine Falcons). Egg contents were filled for pesticide testing and then examined.
Ornithology is a branch of zoology that concerns the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds. It has also been an area with a large contribution made by amateurs in terms of time, resources, and financial support. Studies on birds have helped develop key concepts in biology including evolution, behaviour and ecology such as the definition of species, the process of speciation, instinct, learning, ecological niches, guilds, island biogeography, phylogeography, and conservation.
A marbled godwit being ringed for studies on bird migration
A collection of bird skins, belonging to the family Cotingidae
Geese from a wall panel from the tomb of Nefermaat, Egypt c. 2575–2551 B.C.
Belon's comparison of birds and humans in his Book of Birds, 1555
