Mystery in the lake

Another mystery bird, seen on Como Lake. It was at such a distance that I could not zoom in without becoming extremely wobbly. I'd say merganser, but the head isn't right. Loon? It has a distinctive patch of white on its head, and loons have white throats, don't they? I am extremely new at this bird thing, but it lends a sense of wonder to each new discovery. I always think the bird is somehow aware of me filming it by the way it keeps turning its head.

As usual, YouTube gave me the shittiest choice of thumbnails ever, so I had to come up with my own. I found a picture of a loon and used a glass filter to blur it, then realized that if you look at the image the other way, it's a bit like a gull or other large bird flying against a blue sky with a dark cloud above it. All right, so the cloud is brown! It was an unintentional optical illusion which has nothing to do with the video.