Why does the Swallow-tailed gull have a red ring around it's eye?

The red ring around the eye of the Swallow-tailed gull serves multiple purposes, primarily related to communication and mating. This vivid coloration helps in attracting potential mates by signaling health and vitality. Additionally, the ring may enhance visual contrast, making it easier for the gulls to recognize one another in their social interactions. Overall, the red eye ring plays a crucial role in their reproductive success and social dynamics.