Thanks, everyone. I will work to resolve this new challenge. This discussion has been helpful to me and gave me some ideas.
Let me address a few questions that came in your posts.
He is almost a year and a half. There is no doubt in my mind that he likes to sniff. The first time we saw him at the breeder he was sniffing, and he continues to enjoy it till this day. Is it stress? I don't think it is, in his case.
Now to the question about mixing training and playing. I do formal obedience training with him and we are all business. I let him take off the steam before it, but once we are there we are training. He is focused on me. He is not distracted by other dogs, or smells, even when we do it outdoors. A distraction can happen, like there was an interesting unspayed female recently, but it was clear to me what was going on and I got his focus back with no issue.
Now, the field training is a bit different for us. The main difference is that it is a lengthier ordeal, and we have kids and jobs, and this becomes a part of a family outing for us. I am the one teaching him basics, particular drills, making sure he understands something, and so on. I do that with him at home, in our yard, and at a field next to our home. We live in a semi-urban area, and this field next to our home is a large sports field owned by the town. There is nothing challenging in terms of the terrain or smells of wild animals, but there are smells of other dogs and at this point, he is able to ignore this when we train. It is usually the weekends, when we go to some more challenging terrains to train and we do it as a family. Maybe that means that the distinction between playing and training is not clear, but I am not ready to change this. My husband is the bird boy and I am the handler, and I usually let the kids handle the dog for a few throws. When we train, we are focused on doing it properly, but the whole outing is mixed with fun and play. We don't do many throws, as I don't want him to get bored. We can do more water throws because he is very interested in them.
He loves water and from the start was enthusiastic to retrieve from it. We worked on bringing enthusiasm for land retrieves. Making it fun was important for that reason too. He now wants to do land retrieves, but to bring that out, we relied on activities he liked such as swimming, sniffing, tugging, etc. As an example, I would throw a bumper on land, but he would need to go over a small stream to get it. Currently, I think he is not the best marker as he is doing a lot of hunting, but I am not rushing to fix that because I see his tail up in the air while he is sniffing excitedly to find the bumper. That is one of the reasons why I am cautious to discourage sniffing.
Now, let me explain what actually provoked me to write the post. I felt that we are at a certain point where he can ignore the smells and be focused on getting the bumper and bringing it to me. So, we arrive to train with this group and as he is getting out of the car I see that he is all excited about the smells. I am not sure what it is exactly, but I just take notice. It was announced there is a bitch in heat. OK. She is going to run last. I air him and it looked to me I had his attention. I am getting ready to get to the line and focusing on the things that we are going to do. I hear him whining a bit and I take it as a good sign - he will do it if he needs to wait for a retrieve. I go in first holding blind, ask him to sit, but he is restless and eventually drops on the floor with his face where the other dogs' butts were. I get him to sit again. Then we go to the next blind and the same thing happens. We go to the line and I am working on setting him in the right direction and he just slides and again he is in a down position with his head stuck to a particular spot. It's not sniffing, it is I want to rub in this. In the end, we do the exercise - it was a double - it wasn't so bad, but he dropped a bumper and started sniffing at a particular spot again. So, now having a chance to think about this, I am wondering if there might have been another female in heat that was running before us. On the spot, I was not sure what was going on. I will be better prepared if this happens again.
I am like a driver who just got a license. With no experience, you have to think to pay attention to all sorts of things. When you have driven for a long time, you get somewhere and have no clue what was there on the road - it's all automatic to you.
For us humans, we do not know where interesting smells on that big field are. You only realize there is something once you see all dogs sniffing there. I guess I knew I can expect something like that on his way to retrieve, but have learned a lesson that I need to expect to deal with smells at the line.
Inexperience is my problem, but there is something sweet in all this. I know how it is when you reach a professional level at something - it can get less pleasurable. So, I will enjoy the phase.
Thank you all.