In all honesty, everything I know about diver hunting was learned from BBBD, another guy that I go sea duck hunting with, and by reading this forum, and a small amount of trial and error. Truthfully.... Anything you try CAN work. It just depends on the day, the birds, and the location. Here's the way I look at it.... Everyone sees ducks (puddlers, divers, or sea ducks) sitting in groups together. What not everyone sees, is that they don't FLY together. Sure, you see a group of one specie with the occasional 1 or 2 birds of a different specie mixed in. But 99% of the time Cans fly with Cans, and BB fly with BB, etc. What this means: Ducks are racist to a certain extent. All of them. But none of them discriminate when there is a handy food source or a "safe" place to loaf. In the above spread where long lines lead to a wad, it is my own personal belief that ducks see 1) a food source/"safe place that the wad of decoys has found and 2) Lines of newer ducks who have recently landed and are swimming into the wad. I believe these too things because every time I have hunted longlines.... I have watched groups of one kind of duck land 40 yards outside the spread and swim single file into the spread. I believe in the single specie lines, because I heard BBBD tell me the night before my first ever diver hunt "you watch these divers.. They will fly in from any direction and find the line with there own specie. They will make a sharp turn if they have to, but the will follow that line all the way in to the wad and land." Now, being the skeptic that I am, I felt the same way that you do. I thought to myself "we'll see, I bet that is the 'goal' and not the usual." Then we set out our spread in the morning and hunted divers all day for two days straight. And sure as SH!T, those dang divers did exactly that. All day long. Both days. It was the most surreal thing to hear someone predict how birds would react to our spread, and then watch that prediction be accurate 95% of the time. I was blown away and hooked on diver hunting from that day. Sorry for the long winded reply.
Yard Buck pro-staff trainee