They look a little dark to me - underexposed(?) - probably not, because you ran up against that old problem of photographing something dark like this bird against the snow, which is extremely white. When you have a situation like this with a dark subject against a very light background, I would suggest that you use an exposure compensation of +1 to +1 1/3 stops, or even up to +2 when the subject is is quite dark as this one seems to be.
Do you happen to know what kind of bird they are as they do not look like a bird I would expect to see in the prairies in the Great White North?
WesternGuy