Thayer's Gull Wingtips - Variation
Photo 1. Adult female Thayer's Gull in the Collection at Royal Ontario Museum in Toronto
Photo 1. Adult male Thayer's Gull in the Collection at Royal Ontario Museum in Toronto
Click on photo above or on this link to Thayer's Gull Wingtip Patterns in Howell and Elliott's article
Identification and Variation of Winter Adult Thayer's Gulls in Alula Vol 7 2001.