scwald,
In public lands in area's that get a lot pressure, I would have to say yes elk are getting call shy, not bugling as often during the legal shooting hours, and for sure a lot more cautious on approach when coming in to a call whether it's a bull call or a cow call. Cow calling has become the tend of most hunters because bugling is more successful if your already into the elk and not trying to bring one too you. Bulls are gathering cows for the rut which makes cow calling more appealing to a lonely bull or a bull with only a few cows in his harem. If you get a huge bull to walk away from his cows for a great distance to investigate a call you just might be the worlds best elk caller, it just don't happen. Now if your right in amongst the harem and bugle he will most likely come in hot and ready to fight.
I use my calls in a few basic ways that my help you get in close for the shot. But not all elk act the same way in different area's. It's mostly situation vs. past experience.
Only two reason's I use a bugle.
1st- Early morning locating the bull. Call once to see if anything answers back and if not then don't keep calling. If the bull answers and you didn't get his location then you may have to do it again. But that's when I shut up and go at the bull in a semi circle down wind from him if possible.
2nd- If I have managed to sneak into the bull's harem and he's on the outskirts from me, that's when I'll rip the biggest baddest bugle I can and let him know this is gonna be a fight and I' m not leaving. Sometimes you will push the herd but most times the bull will be on you before you can even draw.
Cow calls have many different uses for me anyway.
1st- I use a cow call more to cover my mistakes than to actually call in a bull. Especially when I'm stalking in on the whole herd. If I happen to make a noise loud enough to cause suspicion then I'll use a small mew. It tends to relax them a bit.
2nd- If the elk see's movement but has no other sense of what it saw they will bark. They didn't smell you but you alarmed them. I will come back with a bark myself like I'm also worried about what's in between the elk and I and if the elk doesn't break for it then do a soft mew to relax the animal. This is less than a 50% chance in my experience but your already busted anyway so trying don't hurt.
3rd- Cow calling a bull, I only call once about every 20 minutes and change position by 50 to 100yds after trying two to three calls. But bulls come in quiet and they know exactly where that call came from. Just make sure he's not there watching you when you do so.
What works for some elk may not work on the next group. There's no absolutes in calling elk and every situation is different. The day they nail that pine box shut on me then I'll be the best elk hunter I ever could have been. Until then I'll keep learning about them.
Good luck to you. You'll learn more about elk from archery hunting than any other method out there. Be patient you'll know when it's time to make a move to get that shot.