I know that Semiahmoo Spit is not in BC, but it is only a few minutes over the border so I decided I would post about my visit to it yesterday (March 10 2012) anyways.
I arrived at the spit in the afternoon, and it being the first time I had been to this location, I did not know where to look first. The side I looked out on first was not open ocean, so there were not many birds (it was the bay). There were a few scaups, some Bufflehead, two kingfishers having a dispute far away, but not much else. I looked out on the other side (open ocean) and was happy with what I saw.
There were many Scoters, some loons (common and possibly pacific) extremely offshore, cormorants, goldeneyes, scaups, buffleheads, and much more. Only one loon (Common Loon) was close enough to shore to see with a naked eye. Here is a photo of that loon:

None of the other birds in the area of the loon were close for photos that were not just ID shots, exept for two Buffleheads and a Common Goldeneye. Here are two photos of a male and female Bufflehead, and another of a male Common Goldeneye.



While I was photographing the Goldeneye and Buffleheads, some other birds moved in. They were a group of Brants, feeding on some aquatic vegetation. I took some photos of them.




While watching the Brant Geese, another bird caught my attention. It was a juvenile Cooper's Hawk, but it was not in a good position for photos. Here is a photo of it anyways.

While all this was going on, every so often a eagle or two would make an appearance. Here is a photo of two young eagles flying above.

I had identified all the birds out in the open ocean, so I checked the bay again. The same birds were present (like scaups, buffleheads, etc.). Having seen all the birds present at that time in that area, I headed in the direction of the hotels. Farther up there were the same things as there were before, so I went even farther in the direction of the hotels. Here there were different subjects, and some of the same ones. By the road there were eagles (3 eagles, two looked to be about 2 years old, the other 4 years old), but instead of flying, they were perched fairly low down. I took a few photos:

Other new birds included White-winged Scoters, near some Surf Scoters (a bird I had seen earlier). Here are some photos of the White-winged Scoters, and one of some Surf Scoters.



As I went closer to the hotels, there were fewer birds on the open ocean, and more birds on the bay side. Farther up, there were more scoters, there were Horned Grebes, Buffleheads, scaups and more. Here are some photos of those birds:




Also near the these birds was at least 2 Red-breasted Mergansers:

OK. So you are probably wondering if I took even one photo yesterday that was not just an "ID" shot. I did. And the birds that supplied those photos were just a bit farther towards the hotel. The first one was a group of at least 11 Black Turnstones. I counted them a few times, first I got 9, then 11, then 13, then 11. They blend in so well with the rocks they were on, so the counts may not really be accurate. Here are a few photos of the turnstones:





Just past the turnstones a single Common Loon that was almost in full breeding plumage caught my eye as it dived. 2 minutes later (yes, that's TWO MINUTES), it surfaced but this time it surfaced right in front of me and was above the water for 20 seconds before diving again. It really surpised me to see how long it could stay under water. The loon provided me with some great photos.





The loon was my favorite part of my trip. Near the loon, a group of Harlequin Ducks was feeding:




It was a great birding trip and I would definitely want to go to Semiahmoo Spit again.