Narrator: Listen to part of a lecture in a biology class. The professor is talking about water fowl.

Almost all of the fourteen varieties of geese are found in the Northern Hemisphere. Like ducks, they make long migrations in the winter, although they do not travel as far as most ducks do. Geese are usually larger than ducks and smaller than swans, but there is a great variation within the family of geese. Some varieties weigh as little as two pounds, while others weigh as much as twenty pounds.
Unlike the case of ducks, it is difficult to distinguish between the female, called a goose, and the male, called a gander, because their coloring is so similar. The males and females do not mate until they are three years old, but when they do, they mate for life. The offspring, called goslings, remain with their parents for one year. Then the young ganders establish their own nesting territory and begin to defend it from [bad word]  These territories are often located in the grassy shorelines that provide the materials for their nests, including grass, twigs, and reeds. The gander stays with the female to protect and raise the young goslings, especially urgent during the first forty to eighty-five days that it takes for the young to master flight.
Many species of geese fly in a vee formation. The group has a leader, and the movement of air by the wings of each bird in the formation makes the task of flying easier for the bird behind it. On long migrations, several geese will take turns leading the group.

Narrator: Now get ready to answer the questions.