This female House Sparrow (Passer domesticus or HOSP ) was caught on March 23, 2008, and dissected. (HOSP are not protected under the federal Migratory Bird Treaty Act, as they are a non-native, invasive species.) This female had already laid four eggs in a nestbox. You can see the fifth egg in the oviduct, forming a lining over the egg yolkd and egg white. A sixth and seventh egg are forming with a yolk in the center of the photo. To the left are another 15 or so smaller "seed" eggs. The female HOSP can cut off this string when she completes a full clutch (HOSP generally lay 1-8 eggs per clutch.)
This photograph is gory, but does do an excellent job of illustrating the "conveyor belt" egg production process. Photo and information from Keith Kridler.
