The first time that Woodstock's mother makes a definate appearance is in the strip from March 3, 1966, where she builds a nest on Snoopy's stomach, and lays two eggs there, much to Snoopy's dismay. The mother then flies away, and is never seen again, leaving Snoopy to raise the two baby birds (one of the baby birds becomes Woodstock, and the other one's fate is unknown).
Although Woodstock's mother is never shown in the strip again, she is mentioned on numerous occasions. A running gag between Snoopy and Woodstock, is that every Mothers' Day, Woodstock goes on top of a hill, waiting for his mother to show up. Unfortunately, she never does. However, Woodstock never loses hope in finding his mother, and often thinks of ways try to to find her. For instance, in the strip from December 31, 1998, when Snoopy shows Woodstock a calendar, and tells the bird that it can show him the date, Woodstock asks if a calendar can show him where his mother is.