On our whale trip we saw many hundreds plus of seabirds, we weren't counting as much as looking and I was also photographing. The seabirds were out feeding with the whales, near Jeffrey's Ledge, a 33 mile long shallow glacial deposit underwater formation that stretches from off Rockport, Mass. to south of Cape Elizabeth, Maine. Because of nutrient rich upwelling from the deeper waters next to the ledge, it's very productive of food (small fish, mollusks, crustaceans) for the whales and other marine creatures. Here's a Greater Shearwater in flight. By far, the most numerous seabirds we saw were Greater Shearwaters. They have grayish brown upperparts, a dark cap and a variable white collar. This one has less of a collar. You can see the narrow U-shaped white patch on the rump.
We also saw a fair number of Cory's Shearwaters, shown here. The yellow bill is quite prominent, a help with their ID.
It ain't easy to photograph seabirds. First of all, you're on a moving boat. We were lucky in that the seas were calm, with no big swells. Some tips, brace yourself against the wall of the boat, keep you knees slightly flexed and plant your feet somewhat widely to steady yourself. Forget a tripod. The boat is crowded, rocking and you have to manuever around people. Use a telephoto lens with image stabilization. I had a Canon 300 mm IS lens with a 1.4 teleconverter (giving me 420 mm) and a Canon Mark II camera. If you can hand hold the heavy 500 mm lens or the 300 mm f 2.8 lens then good for you, they are too heavy for me.
Here's a Greater Shearwater taking off, love the pinkish feet.
Another species we saw was this Sooty Shearwater, an easy ID because of its almost all over sooty color, except for the whitish on the underwing primary coverts.
Here's what it really looks like, with lots of little shapes bobbing on the water. These are Greater Shearwaters, but you need to look carefully at each group of birds and all birds flying by to ID them.