Pacific Loon juvenile with Common Loon

Good comparison of many of the features just discussed. I often think of Pacific having a "snaky" look to the head and neck, in many postures reminding me of a cobra!

Remember there are many variations in basic-plumaged Common Loons. Especially at a distance, in poor light, and/or with quick views, a Common can simulate other species. Don't work too hard to turn an odd Common into another species -- usually when you see the "real deal," it just "pops" with little doubt.