A couple of weeks ago I was able to see some chicks of yellow-legged gulls (Larus michahellis) at sunset, in Bayona (Galicia, Spain). At their young age, these seagulls have a mottled brownish plumage, which later turns white, with gray wings.
I looked specifically at a group of three chicks that waited on a rock to which mother gull brought them something to eat ... But they went to sleep with nothing to carry to the mouth. One of the chicks, who had already curled up to sleep with his brothers, stood up to approached his mother, touching its beak. I guess he was just checking if she could give him something to eat. As the mother had nothing to offer him, she flew away, and the chick went back to sleep with his brothers.
In one of the photos of this set, mother gull is croaking, her beak fully open. When they saw strangers approach, all the seagulls in the area began to croak incessantly, as if they were giving the alarm to a possible threat to their chicks.
A curiosity: when the chicks fell asleep, the adult gulls disappeared. The plumage of the chicks was a good camouflage, and unless you had seen them before, it was difficult to distinguish them from the vegetation around them. However, the adult gulls, with their white plumage, stand out a lot on that vegetation. Maybe they will leave so as not to betray the place where their chicks sleep? I am not an ornithologist and I do not know the answer.