Pacific Loon juvenile

Aged as juvenile by neat pattern of light edging to upperparts. Note thin straight dark bill and relatively small head with more sloped forehead lacking a pronounced bump. Dark of upper face nearly surrounds eye without white penetrating above eye like often seen with Common. Adults typically show a dark chinstrap, but juveniles often have either no strap or just a hint at the sides.

Pattern of the interface of light and dark on the neck-side is important. Note lack of a posterior indentation, giving an unbroken line unlike the zigzag of Common. Adult Red-throated Loon can have a a straight defined border, though has more white on the neck and face (extending above eye), different bill shape and posture, and would not have barring on the upperparts.