Two white spots

Many feathers are difficult to identify, but some are relatively easy.  Do you recognize this one? 

 

The two white spots against the dark background are distinctive.  Any guesses?

This is a loon feather.

On the East Coast I wouldn't have hesitated to call it a Common Loon feather.  But after taking this picture tonight, I realized that I wasn't certain how to distinguish a Common Loon feather from a Pacific Loon feather.  I'll have to do more research about that, or if you know the answer, feel free to write in. 

For pictures of a Common Loon at Spud Point Marina, including some white-spotted feathers, see the post from 3 April 2012.