Before modern binoculars and cameras made it possible to observe birds closely in the wild, many people collected eggs as a way of learning about birds. Serious collectors called their avocation "oology" and kept meticulous records for each set of eggs: the bird's name, the species reference number, the quantity of eggs in the clutch, the date and location where the eggs were collected, and the collector's name. These documented egg collections, which typically date from the nineteenth and early twentieth centuries, now provide an important baseline from which to measure changes in the numbers, distribution, and nesting patterns of many species of birds.

In Oology and Ralph's Talking Eggs, Carrol L. Henderson uses the vast egg collection of Ralph Handsaker, an Iowa farmer, as the starting point for a fascinating account of oology and its role in the origins of modern birdwatching, scientific ornithology, and bird conservation in North America. Henderson describes Handsaker's and other oologists' collecting activities, which included not only gathering bird eggs in the wild but also trading and purchasing eggs from collectors around the world. Henderson then spotlights sixty of the nearly five hundred bird species represented in the Handsaker collection, using them to tell the story of how birds such as the Snowy Egret, Greater Prairie Chicken, Atlantic Puffin, and Wood Duck have fared over the past hundred years or so since their eggs were gathered. Photos of the eggs and historical drawings and photos of the birds illustrate each species account. Henderson also links these bird histories to major milestones in bird conservation and bird protection laws in North America from 1875 to the present.