Call Less; Call Quieter
Slow-bird days are lazy days for ducks, and this dictates a softer, less-aggressive style of calling than you would use on a blustery new-duck day.
On calm, cloudy days, I use a quiet, raspy call, and I blow it sparingly. I hail-call to get passing birds' attention, and then I back off as they begin circling. I may blow a short comeback as they slide downwind, and sometimes I might chuckle and make a few quiet quacks, but I'm not compulsive. On slow-bird days, a demanding style of calling will usually scare ducks away. (Some days, as in the one described above, no calling is better than even minimal calling. Experiment to see what works best.)
Keep Covered; Keep Still
Good camouflage is a necessity on slow-bird days. Again, when it's overcast, there are no shadows, and low-flying ducks can see down into blinds, boats, brush, etc. It's easy for them to pick up a face looking up or a hand reaching for a shotgun.
Keep your blind well brushed throughout the season, especially the shooting hole. As the season progresses and cover is beaten down or blown off a blind, add more periodically to keep hunters hidden.
Make sure hunters' clothing blends into the natural surroundings – no bright colors. Also, a face mask is a good idea to hide hunters' shiny faces.
Sometimes ducks are easy to pull in when the weather is right and new flights are arriving. But catch a slow-bird day with ducks that have been called to and shot at until they are super wary, and decoying them in close can seem like Mission Impossible.
But it's not! Slow-bird days may not provide fast action, but they can be better than most hunters expect.
When I left our blind toting my four ducks, I had high hopes for the next morning's hunt. My new tipper decoy had passed the test. Now, I knew that if it was one of those days when ducks were circling out of range, almost with a taunting attitude, I'd give my goose a couple of hard tugs and get ready. Chances are their flaps and landing gear would come down, and another duck or two would make a splash landing!