Pray to the hunting gods
Actually my answer was kinda serious.If they're leaving from feeding they are heading to water.So you just may have to move.
Get a high powered sniper.
There isn't enough to your question to know how you hunt, so giving you a "serious answer" ends up being mostly guess work. My "guess" is that you weren't hunting the feeding field so you missed them there. And when they left, you weren't offering them the safety and seclusion they prefer in a rest area, and so you missed them there as well. The fact is, if you conceal yourself well enough at one spot or the other, you probably don't need a call to do what is commonly referred to as "pass shooting". You also don't mention using decoys. If you have none, how do you expect ducks to come in to ducks calling which they cannot even see? To be really successful requires a combination of more than just "good" calling techniques. Without proper concealment in a blind of some kind and wearing appropriate camouflage, no amount of calling (good or otherwise) will Pied Piper ducks OR geese to their demise. A GOOD presentation of decoys placed in proper formations that look natural and which show openings that draw the birds into their midst is a GREAT benefit. Calling adds to the attraction when birds hesitate to come in to otherwise silent decoys. Add these to a great blind set-up in a good location and you WILL score well. Rambling and wandering around the country side trying to be at the right place at the right time without proper preparations and equipment is a waste of time. Blowing on a call without good camo, the blind, and the decoys is usually just a waste of breath.