Oology

Oology is a specialised branch of ornithology concerned with the scientific study of bird eggs, bird nests, and breeding behaviour. The term is derived from the Greek oion, meaning ‘egg’. Historically, the term has also been applied to the hobby of collecting eggs of wild birds, a once-popular pastime now prohibited in many countries due to its harmful impact on bird populations. The field has evolved from nineteenth-century natural history pursuits into a modern discipline focused on conservation, avian reproduction, and ecological research.

Scientific Development of Oology

The scientific study of bird eggs gained momentum during the nineteenth century, particularly in Britain and the United States. At a time when high-quality optical equipment was not widely available, examining eggs often proved more practical than studying birds from a distance. Collectors and naturalists frequently obtained eggs by climbing to nests or shooting adult birds, practices that were then regarded as legitimate scientific methods.
As ornithology developed more rigorous observational and ecological approaches in the twentieth century, oology gradually shifted from a mainstream scientific activity to a narrower field of reproductive biology. The discipline nevertheless played a crucial role in some significant scientific discoveries. In the 1960s, for example, the naturalist Derek Ratcliffe compared historical egg collections with contemporary samples of peregrine falcon eggs. His findings revealed widespread eggshell thinning, which helped establish the link between pesticide exposure—notably DDT and dieldrin—and the decline of British birds of prey. This work exemplified the lasting scientific value of earlier egg collections, even as egg collecting itself declined.
By the mid-twentieth century, oology had become largely overshadowed by modern ornithological methods, although the data preserved in museum archives remains invaluable to researchers studying environmental change, pollutants, and reproductive adaptations across avian species.

Egg Collecting as a Hobby

From the late nineteenth century into the early twentieth century, amateur egg collecting was a widespread hobby. Enthusiasts at times went to extreme lengths to obtain rare specimens. One well-known anecdote recounts the collector Charles Bendire breaking his teeth while retrieving an egg he had placed in his mouth for safekeeping during a precarious descent from a tree.
Collectors frequently traded specimens and organised themselves into clubs or societies. The British Oological Association was established in 1922 by Walter Rothschild and Francis Charles Robert Jourdain as an alternative to the British Ornithologists’ Union, whose leadership disapproved of the practice. After Jourdain’s death in 1940, the group became known as the Jourdain Society.
Despite its popularity, egg collecting gradually drew criticism for its detrimental effects on bird populations. By the mid-twentieth century, it had ceased to be regarded as a respectable scientific pursuit, and its status increasingly shifted towards that of an illicit activity.

Legal Restrictions and Wildlife Protection in the United Kingdom

Legislation in the United Kingdom progressively curtailed egg collecting. The Protection of Birds Act 1954 made it illegal to take eggs from the wild, and the Wildlife and Countryside Act 1981 further strengthened protection by prohibiting possession of any wild bird’s egg unless it could be shown to have been collected before 1954. The sale of eggs, regardless of age, is prohibited.
Although legal restrictions reduced the practice, illegal collecting persisted underground into the late twentieth century. Enforcement challenges remained, especially as fines were initially modest. The Countryside and Rights of Way Act 2000 introduced potential imprisonment of up to six months for possession of wild birds’ eggs, greatly increasing the penalties.
A number of individuals have since been prosecuted, imprisoned, or repeatedly reconvicted for illegal egg collecting. Notable cases include that of Colin Watson, a prolific offender who died in 2006 while attempting to reach a nest. Others have been convicted for possessing hundreds or thousands of illegally collected eggs well into the twenty-first century.
The Royal Society for the Protection of Birds (RSPB) has played a leading role in combating wildlife crime. Its investigative unit works alongside police forces to track offenders, gather intelligence, and protect nests of rare species. At one point, staff received training from members of the Brigade of Gurkhas in camouflage and surveillance techniques to counter sophisticated illegal activity.
Owners of old collections must maintain evidence demonstrating that their specimens predate 1981. Museums rarely accept donations unless accompanied by precise collection data, such as date and location, which gives scientific value to the material. As a result, many private collections have limited legitimate avenues for disposal, and museums have ceased displaying egg collections to avoid encouraging illegal interest.

Legislation and Enforcement in the United States

In the United States, egg collecting and possession are also restricted. Federal laws including the Migratory Bird Treaty Act of 1918, the Lacey Act of 1900, and the Endangered Species Act impose strict protections on many species. Violations can be treated as criminal offences, with penalties depending on the species involved and the nature of the offence. Unlike the historical context of the nineteenth century, scientific research today requires rigorous permitting processes and ethical standards.

Methods of Egg Collecting and Preparation

Traditional collecting typically involved removing the entire clutch of eggs from a nest. To prevent decay, eggs had to be ‘blown’—their contents removed through a small opening drilled in the shell. Freshly laid eggs were preferred because they were easier to blow than those at later stages of incubation. Similar techniques are used in contemporary craft traditions, such as egg decorating with domestic bird eggs.

Major Research Collections

Large historical collections preserved in museums and research institutions continue to serve as scientific resources. Notable examples include:

• Approximately 610,000 eggs in the United Kingdom.
• Around 520,000 eggs in the United States.
• Collections in Melbourne, Australia, numbering roughly 190,000 eggs.
• About 150,000 eggs in Washington, D.C.
• A Toulouse collection of over 41,000 clutches totalling 135,000 eggs.
• The former Museum of Comparative Oology in California, which once held nearly 800,000 eggs across 190,000 clutches.
• Approximately 11,000 sets from 1,300 species in Santa Barbara, California.

Oologists and Notable Contributors

Numerous naturalists and authors contributed to the literature of oology. Among the most prominent were:

• A. J. Campbell, whose works on Australian nests and eggs were foundational in regional ornithology.
• Charles Bendire of Washington, D.C., author of Eggs of North American Birds (1890), known for his extensive contributions to North American oology.
• Thomas Mayo Brewer, noted American ornithologist and contributor to History of North American Birds. He has been regarded as an influential figure in American egg study.
• Henry Seebohm, author of Illustrations of Eggs of British Birds (1856).
• Frank M. Chapman and others who produced field guides and references that shaped the study of North American avifauna.

Publications and Cultural Representations

Oology has inspired a substantial body of literature, ranging from identification guides to comprehensive catalogues. Some notable works include North American Oology (partially published in 1857), Nests and Eggs of Australian Birds, and various illustrated guides to British and North American species.
The subject also appears in popular culture. In P. G. Wodehouse’s novel The Pothunters, a schoolboy’s pursuit of rare eggs forms a comedic subplot. A 2007 episode of the television series Midsomer Murders, titled Birds of Prey, centres on illegal egg collecting. More recently, the artist Andy Holden, in collaboration with ornithologist Peter Holden, created a series of exhibitions titled Natural Selection (2017), exploring the history, motivations, and moral complexities of British oology through installations and film.