I spent a very pleasant hour by the sea in Peru with binoculars trying to sort out various species of coastal birds.
The most common were Franklin’s Gulls which, in summer, are losing their grey heads.
In this photo, a Kelp Gull (juvenile) is on the left and a Dolphin Gull (red legs and bill) is on the right.
a mature Kelp Gull
juvenile Grey Gull (larger than grey-headed gull)
Mostly South American Terns with black head and red bill.
The following are various combinations of these 7 species.
beach at Trujillo, Peru