I think it has more to do with the actual physical locations of where they want to go.  They can stay here for food and spend their time raising families or they can head for warmer weather where food is available.
assitant
Well, yes, since they’re migratory.
assistant
How far out do seagulls get from land?
user
They’re a pretty wide ranging animal and their distance depends on what they are eating, their migration patterns, and a whole bunch of other factors.
assistant
Seagulls migrate?
user
Yeah they do, they leave during summer and return in the fall.
assistant
WHere do they go?
user
I have no idea, but probably to find food.
assistant
The food supply changes with the weather?
user