Just for thought, I live in North Alabama where we have hunting zones, opening from Oct1-Jan 27 and Oct15-Feb 10 for bow hunting. Gun season opens Nov 7-Jan27 and Nov 21-Feb 10. From Oct till Gun season opens I see deer in daylight hours regularly but bout a week after gun season opens the number drops big time. I have always thought, it’s because guns popping, more human scent, noise and more human contact. Could it be they go dark because of the shorter days and well longer nights? In Sept. - Oct we plant food plots and Acorns start dropping in big numbers and with mild temps there is a massive amount of food, including corn and natural browse. I have read deer eat four times a day but with the long nights and short days maybe they really load up at night and can tuff it out in daytime until dark. They seem to start showing up better in daytime, late Jan with the season still going on. I’m totally excluding the Rut that is another ball game, just feeding habits. What say you.
Deer in the deep south are primarily nocturnal. I have probably hundreds of thousands of trail cam pics that prove this. 365 days a year, with or without pressure, the bulk of deer activity is at night. I would assume the same is true for deer in other parts of the country.
Since I'm also from Alabama, I feel like I can explain what you're observing in particular quite well. You say deer are active during daylight during the summer. I would agree for the most part. The bulk of the activity is at night, but our does are still recovering nutritionally from dropping fawns in the summer and nursing. They have higher caloric needs and feed accordingly. I personally do not witness much if any mid-day movement during this time frame. I attribute this to the fact that it's often 90 degrees outside during the heat of the day. Deer don't sweat. Why not feed at night when it's cool? Or at least very early or very late in the evening and on cooler days.
Pressure ramps up DRAMATICALLY once rifle season hits. Harvest records back this up. Alabama is a strong gun state and most of the hunters kill most of the deer with a rifle. At this point, it begins to make absolutely 0 sense for a deer to travel during the daylight. Predators are in the woods, but only during the day. Food is in the woods 24/7. They can see and hear just as good in the dark as they can during the day, and they probably don't suffer a meaningful drop in visual acuity. What would you do if a monster was hunting you and he only came out from daybreak to 12pm? Would you wait to run errands until after lunch once you figured out that little pattern?
There's an almost useless half truth the the thought that "they're not nocturnal, you're just not where they are." Deer don't get the leisure of 8 hours of zonked-out sleep like we do. That privilege is reserved for apex predators. Deer mainly microsleep and are never really "off." Additionally, since they're a large mammal subsisting off of very low caloric density food, they have to eat a lot. So they will browse during the day and sip a little water. BUT...they are ruminants. So they're quite capable of gorging themselves and then digesting it at their leisure in a thicket somewhere. And they get the bulk of their water from their diet. And here in the deep south there is no shortage of thickets that have food, cover, and water. We don't have anything to force them into one area. We're not an ag state. We export timber and always have. So you have millions of acres in the state that are big woods or clearcuts, and both provide plenty of food and the kind of cover that you are not going to penetrate without tipping your hand. You're not going to be able to home in on a big bucks bed here like you will be able to in other parts of the country where there is less cover. Ask Eberhart what he thinks about hunting the big woods in his home state. He quit because it's just low odds. Big woods are almost always lower odds than mixed ag or suburban hunts because deer aren't forced to bed in one location or travel one specific route. If you put a little pressure on them, they can move 100 yards and be happy as larks.
I honestly quit hunting Thanksgiving to New Years after reading Dr. Sheppard's book. For Alabamians, with our stupid-long season...it just doesn't make sense. There's too much cover, too much food, too much pressure, and the deer have very little reason to play your game. It's possible to kill deer during this timeframe, and I guess it's also possible to sell hot chocolate in the summer. But it's not a good use of your time and energy. The exception is the section of the state where the rut hits during that timeframe, and very cold days. Which brings me to...
That little late-season boost in activity we get. It's a combination of 2 things. The rut, and dwindling food supplies combined with increased caloric needs. We have a mid-January to early-February rut here in my part of the state and many others. Obviously, that increases deer movement
both during the night and during the day. All that running around burns a lot of calories. Our coldest weather usually hits during January. If you can't burn wood to keep warm, you have to burn more calories. Colder weather and more physical exertion means you eat more, and the rub is by that time of year the woods are largely barren. Deer don't starve to death in Alabama during the winter, but they definitely feel the belt tightening. Most of the good browse is gone. Most of the acorns have dropped and rotted. My dad and I always notice a big uptick in plot and feeder activity once this happens. If you wanna know when it will hit, find a woodline where you can get a pic of the canopy and understudy and take a picture of it once a week throughout season. Go back and look at them and it's pretty stark when the woods open up and everything turns grey and brown and tan. The only thing green where I'm at right now is mistletoe, conifers, palmetto, and live oaks.
Everything deer hunting revolves around food, cover, and the desire to breed. The rut only makes up a couple of weeks of our season. And the rut is honestly going to mainly be dictated by what the does are doing, and since they don't suffer from much of a sex drive they're still going to be focused on eating and hiding! The more your deer are eating and the less they're hiding, the easier your life is going to be.