We see this bird here as well the whole year round, but mainly in spring and autumn when they migrate. It's one of the most reported birds in Suriname. It's amazing that they travel such vast distances, all the way from Chile and Argentina to Alaska.
I believe that they are relatively short distance migrants, with the more northern birds wintering in more northern areas, and the more southern birds going yet farther south, but I could be wrong in this belief. They breed over a very broad area.