#13 These birds live in flocks. Sometimes they number thousands of adults with offspring.
#14 There are sedentary species of gulls.
They are most often found near open water such as the endless sea or ocean. These birds are sedentary.
Other species choose temporary dwellings: some kind of lake or river. They live there at certain times of the year. After living conditions lose their comfort, these gulls fly from place to place in search of a warm sea place for habitation.
#15 There is also a third option for the existence of gulls.
These remain where they are used to, despite the unfavorable environment. And the usual food is exchanged for urban food waste.