I found another reference to the Loon in my Birds of Alaska guide. Quote: Arctic Loon 28". See Pacific Loon. Breeding: White patch on rear flanks (visible just above waterline when swimming), green sheen on throat (difficult to see), smoky gray on back of neck. Winter: White Patch on rear flanks. Similar species. Very difficult to distinguish from the Pacific Loon, but Pacific Loon LACKS WHITE FLANK PATCH. In summer etc. ----