Common Loon adult

Thought an adult based on uniformly-dark upperparts. Note heavy bill, with mandible mildly upcurved and maxilla slightly down curved; bill is pale gray with dark culmen to tip. Ill-defined whitish is seen around eye. Neck-side pattern is important, with pale indentation extending toward the rear of the neck about midway; as in this bird, depending on position this can briefly be less obvious and appear straighter, so you need to watch the bird if there is a question.