Oology, or oölogy is the branch of zoology that deals with the study of eggs, especially birds' eggs. It can also be applied to the hobby of collecting wild birds' eggs (which is now illegal in many jurisdictions). Oology includes the study of the breeding habits of birds, and the study of their nests. (The study of birds' nests is sometimes called caliology).
Birds' eggs are conveniently classified as marked or unmarked, according to the ground color. Birds which lay their eggs in holes in trees or in the ground almost always have white, unspotted eggs. Birds which build in trees generally have blue or greenish eggs, either spotted or unspotted, while birds that build in bushes, near the ground, are likely to lay speckled eggs.
While the collection of the eggs of wild birds by amateurs was considered to be a respectable part of ornithology
in the 19th Century
and early 20th Century
, from the mid 20th Century onwards it was increasingly regarded as being a hobby rather than a scientific discipline. As legislation, such as the Wild Birds Protection Act 1954
in the United Kingdom
, made it impossible to collect eggs legally, the practice of egg collecting, or 'egging', continued as an 'underground' or illegal activity in the UK and elsewhere. Collectors can become pathologically obsessed with their hobby and, in the UK, following the enactment of the Countryside and Rights of Way Act 2000
, risk imprisonment for up to six months for the possession of the eggs of wild birds.
When collecting eggs, normally the whole clutch of eggs is taken. Rarer species of birds may be targeted. Because eggs will rot if the contents are left inside, they must be 'blown' to remove the contents. Although collectors will take eggs at all stages of incubation, freshly laid eggs are much easier to 'blow', usually through a small, inconspicuous hole drilled through the side of the eggshell.
- Thomas Mayo Brewer, (1814-80), an American ornithologist, wrote most of the biographical sketches in the History of North American Birds, by Baird, Brewer, and Ridgway (1874-84). He has been called "the father of American oölogy". He wrote North American Oölogy which was partially-published in 1857.
- T. G. Gentry, Nests and Eggs of the Birds of the United States, (Philadelphia, 1885).
- Oliver Davie, Nests and Eggs of North American Birds, (fifth edition, Columbus, 1898).
- William Chapman Hewitson, Illustrations of Eggs of British Birds, (third edition, London, 1856).
- Alfred Newton, Dictionary of Birds, (New York, 1893-96).