ha, yes, I was being lazy, I probably should have checked some images online or in a guide book before commenting! Agree, Least Sandpiper has those white spots and lack of rufous head pattern and just realised the location is Ottawa!
The leg colour on Least Sandpiper is often hard to see if they are messing around in mud (as this one is). But the warm brown plumage rules out Semipalmated, which is the only other "peep" likely to show up in Ottawa. I agree with Rafael - Baird's would show a much longer primary projection.
Tricky one but this is indeed a Juvenile Least Sandpiper. The combination of fairly dense streaking on the face and chest helps a little with the ID, but is not as extensive as on an adult Least in August plumage. The tapered downward curved bill becomes very pointy at the tip, more so than on Western or Semipalmated, and the clincher is that in addition to these other factors, all of the coverts are orange and fresh with scalloping (pale fringes) proving it as a juvenile. Juvenile western would mostly have orange upper scapulars (occasionally some lower scaps and tertials). The whole wing of this bird is orange in other words making this a Juvenile Least.
Western is the confusion competitor here. Bairds would be much longer winged and of a bulkier build, also showing a thicker bill and blunter tipped bill. Semipalmated only get orange as adults, and again bill shape is all wrong for them here.