Cherry,
The first bird is a Yellow-legged Gull L. (c) mongolicus. Pale upperparts, very little streaking around the head, large white mirror in p10, and pinkish-yellowish legs.
The second bird is a Vega Gull, based on the smaller mirror on p10 and purer pink legs. The adult chasing the merganser is also a Vega Gull.
Geoff