Spotting birds and marking falls is an excellent trait to have in your retriever. You want her to retrieve by sight whenever possible and practice, practice, practice to make her a more accurate marker. BUT she also needs to learn to use her nose. Simple and easy place to start, play fetch at night when it is dark out so she has to use her nose. Little more complicated approach requires a friend to throw for you from a distance. Have him get the dogs attention, throw a dirt clod and then you send your dog to fetch the bird. After the dog has hunted the area by sight and not found the bird, have him slip a bird in there without the dog seeing (yeah, it is a bit tricky) and then encourage the dog to recheck the area and she'll find it with her nose.
Also, do you work on getting her to run trails at all. Drag a trail that is straight at first, then L shaped and working to more complicated and longer with a fresh bloody bird and teach her the "track it" command. She'll have to use her nose to find the bird. Make it easy at first so she wins and make a seriously big deal out of finds that require scenting. Be aware that not all dogs will run a track nose down right over it. My best competition dog nearly always ran a track about 10 yards downwind of it with her head up but she zigged and zagged whereever the trail did so it was obvious she was tracking and not just trying to airscent the target at the end of the trail. Let her work out her style and reward that nose when she uses, it will kick in.
