Welcome to the Richter Museum of Natural History’s Online Guide to Wisconsin Bird Eggs
This searchable database is designed to assist in the identification of bird eggs for species that breed in Wisconsin and nearby states. Resources include color photographs of eggs, descriptions of nests and clutch size, egg measurements, and breeding distribution maps. Species nomenclature follows the most recent Checklist of North American Birds published by the American Ornithologists' Union. Images and descriptions are available for 250 species, including a few that breed in neighboring states and are likely to breed in Wisconsin and one extinct species (the Passenger Pigeon) that formerly bred Wisconsin.
Using the Database
In order to identify an egg you need to have more information than you might realize. There is a great deal of overlap in egg coloration and size, particularly in closely related species. There is also variability in color and pattern even within species. If you find an egg you want to identify, you should consider the size, shape, color, and sheen (glossy or matte) of the egg itself. But you should also note the habitat that you find it in, the kind of nest they were found in, and the clutch size (number of eggs in the nest), in order to make the best identification.
Searching our Online Guide to Wisconsin Bird Eggs involves a process of elimination, beginning with your best guess from a visual list. You can search by Family, Group (ducks, finches, etc.), Genus, Species or Common Name. Note that our database is not searchable by egg shape or color because there are too many variables to consider to narrow the search to just a few likely species. For example if you tried to identify a 20 mm long white egg with brownish speckles you would find that seven species of warblers have eggs that fit this description. The search results will take you to a selection or group that includes photographs of eggs along with descriptions of the eggs' size, shape and color. Species descriptions also include information about clutch size and the species' geographic range from the Wisconsin Breeding Bird Atlas. An image showing eggs of related species is provided for comparison. Most of the egg sets pictured here are from the egg collection of the Richter Museum of Natural History at UW Green Bay. We thank the Field Museum of Chicago for photographs of eggs of Philadelphia Vireo and Connecticut Warbler. We have taken great effort to standardize and correct egg colors. Be aware however, that egg color can vary among individual birds and colors form the same digital image can vary depending on your personal computer settings and type of monitor.