I know Clover Point can be a good place to see Harlequin ducks in Victoria, and I've ALWAYS found seagulls there!

(Oystercatchers, black turnstone and sandpiper-types can sometimes be found, depends on the tides.) I mention Clover Point since it's easily accessible by transit (it's an easy walk from Beacon Hill Park). I've also walked from this location to Ogden Point (a bit of a distance, but enjoyable to be by the seashore if the weather holds up), where we saw sanderlings on the breakwater (and of course cormorants too -- may have seen a loon, can't clearly remember).