Figure 1. Not a good photo, but shows the structure of the bird well in a somewhat alert position: very stocky heavy-keeled (or "potbellied") look with smallish round head.
Figure 2. Notice the very large chunky appearance of the bird, somewhat short, rasberry pink legs, dark slaty-blue mantle, rounded head with dark "mascara" around the clear whitish-yellow eye, and small bill appearance due to very slight gonydeal angle.
Figure 3. Slaty-backed amongst Thayer's, Glaucous-wingeds, Herring, and various Glaucous-winged hybrids.
Figure 4. In this photo you can clearly see the black tail with a white tip.
Figure 5. Very wide yawn! Pretty fierce looking!
Figure 6. In this photo notice the blurry, fine streaking on top of the head. Also notice the pale inner webs to some of the primaries and secondaries (?)
Figure 7. A better look at the pale inner webs and "spurs" on on the left wing while the bird preened. I think P5 is the most proximal--and most broadly--white tipped primary, with P9 being the distal-most white tipped primary.
Figure 8. The best open wing photo I could get of the bird. On the left wing you can see a couple of pale inner webs but the primaries are folded over each other pretty well. Notice on the right wing that the inner webs seem to be rather light. P10 has an obvious small white mirror.
Figure 9. Cropped left wing shot
Figure 10. In this photo you can see the brownish mottling on the underwing coverts. Notice the slaty feathers at the base of the wing.
Figure 11. Nice look at mostly black tail. That is not the Slaty-backed's head in the photo!
Figure 12. Quiz photo..... Yup, it's a Slaty-backed under water!
Figure 13. An overexposed photo, but it gives the impression of what the bird looked like in partial sunlight towards the end of the observation.