Habits as other large alcids. Winters closer to shore and is the alcid most readily viewed from land. ID: Big-headed and thick-necked with longer tail than similar species. Striking ridged bill with white lines. Adult at 4 years of age, when has larger bill with more ridges. Male larger than female. Young birds have smaller all-dark bills, broader and blunter than in TBMU. Nonbr face pattern intermediate between COMU and TBMU. Black upperparts. In flight 3 large alcids similar. Use upperpart color, face pattern, and bill shape for comparison. Many birds best left unidentified.