The second Friday of October has been designated as World Egg Day, with a focus on eggs as a food source. But during the late 19th and early 20th century, collecting wild birds eggs was  a popular hobby. Many museums and their collections originated during this time, and many people displayed natural history objects in their homes. Collecting natural history objects — such as bird eggs — became a popular hobby. Egg collectors were fascinated by the variety of sizes, shapes and patterns seen in eggs. The hobby inspired magazines and a system of egg dealers and traders around the world, with rare eggs fetching high prices.

The interest in eggs also stimulated much scientific research, called Oology (or oölogy), a branch of ornithology studying bird eggs, nests and breeding behavior. Eventually, most private egg collections were given to museums so they could be preserved for future generations to study. It’s now illegal to collect wild bird eggs in the United States as well as in England, but the eggs collected decades ago continue to provide detailed data for scientific researchers.

The Delaware Museum of Natural History has the second largest collection of bird eggs in North America, with more than 36,500 clutches of eggs and associated data. Many of the eggs date from 1900 or earlier, and are a valuable record of the diversity of bird eggs as well as representing historical information about birds and places that have changed dramatically over time. Scientists from around the world use DMNH’s collection in their research.

This egg, from the extinct elephant bird, is one of the largest eggs in the world.

This rare egg, from the extinct elephant bird, is one of the largest eggs in the world. It’s on exhibit at the Delaware Museum of Natural History.

A sampling of the collection is on exhibit, including a rare egg from the extinct elephant bird contrasted with smaller eggs, including a tiny hummingbird egg. The elephant bird, which became extinct around the 17th century, had been the largest bird alive before its extinction, and its eggs are the largest bird eggs currently known.  DMNH’s elephant bird egg is mentioned on this Wikipedia page as one of only a few intact elephant bird eggs currently in collections.