If they live in a city where they can get food from people, they may not bother to fly south. They can handle some cold, as long as they have enough food.
They fly north again in Spring because in the north, plants and animals are particularly abundant in Summer due to the longer days. So this makes the north a good place to raise their goslings.
Since we haven't been able to get geese to talk, we can't ask them that question.
We can ask ourselves what the advantage is for many, many bird species to go south in the fall and avoid harsh winters and low food. They then can spend time in warmer climates. The following spring they return again and become breeding summer residents.
We can also answer partially how they do it, with several mechanisms researched.
To get to the other side?
