As long as it doesn't rain, the seeds will float for several days. I'm using black oil sunflower seeds from the birdseed section of Tractor Supply. Not sure if that kind makes a difference but they work so well I haven't had the desire to try anything else. I get a 20 or 40lb bag and I keep them...
FWIW: Last year I cleaned 45 mice and 47 gophers out of my rural Michigan property with a very simple bucket method. 5 gallon bucket with 3 gallons of water. Pour black oil sunflower seeds on water surface until covered. 3" x 4' wooden ramp (pine, osb, whatever) with two screws through one end...