Loon question..common vs yellow billed

[Usha]

Saw this very deep diving loon today in maricopa county, Arizona. Saw it come up only once in 30 minutes when I took photos. Bill looked yellow but thought it was because of morning sun. Common loons are there and saw a few. Since this loon was a deep diver, went back to same location and spent 45 minutes only to see it dive but didn’t spend much time on water to get photos. Enclosing photos I took the very first time I saw it. I am thinking it could be yellow billed based on photos but it would be mega rare here. Appreciate any comments,suggestions,ID.

[akandula]

This is a Common, for the following reasons:

1. Entirely dark culmen (vs outer half of bill of a Yellow-billed Loon entirely pale)
2. Decurved culmen (vs straight/recurved on a Yellow-billed)
3. Small amount of chin feathering (vs greater anterior extension of chin feathering in Yellow-billed Loon, until posterior edge of nostril)

Edited January 26, 2020 by akandula

[Usha]

5 minutes ago, akandula said:

This is a Common, for the following reasons:

1. Entirely dark culmen (vs outer half of bill of a Yellow-billed Loon entirely pale)
2. Decurved culmen (vs straight/recurved on a Yellow-billed)
3. Small amount of chin feathering (vs greater anterior extension of chin feathering in Yellow-billed Loon, until posterior edge of nostril)

Thank you