The bill is too slender and weak for Ring-billed, its mantle is far too dark mid-grey and its head shape too smooth and rounded (more angular in Ring-billed, suggesting a bigger gull).

• 对环颈鸥来说，问题鸟的嘴部太细太薄，鞍部在中灰色中太偏暗色，而且头形太过平滑呈圆形(环颈鸥应较呈角形，暗示为较大型的鸥鸟)。