Ruffies in north-central Alberta are definitely more active during the early morning hours and the 2-3 hours before and up to 1/2 hour after sunset. Like many of you, I've seen and bagged birds at all hours of the day - it's just that they seem more numerous at the beginning and end of the day.
I don't think I've seen (or heard) more birds during any given part of open season, but you see more of the ones you'd only hear at the beginning of the season, once the leaves are off the trees.
Two weekends ago (opening day), I went out, but could only spend a couple of hours hunting late Friday because it rained hard all day Saturday (no Sunday hunt in our area). I got none.
Last weekend, I went out again. Got to the covert at 4:00 PM and had 2 in the bag within the hour. Finished the day with 3. Saturday was hot and dry. Spent from 2:00 PM to sunset hunting the whole time. Ended up with one on Saturday (bagged it in mid-afternoon).
My hunting partner and I have been hunting the same area for about 15 years, now. We've been trying to define ruffie behaviour that whole time and have succeeded only in coming up with a few generalizations. The only fact that is carved in stone is that nothing about ruffie behaviour is carved in stone - too many variables, I guess. Sharptail are significantly more predictable.
SS