The rattle of the dinner bucket does more to call my bunch than all the whistling and yelling in the world. I have no idea how they can hear that when they 'can't' hear me yelling and whistling but one tiny little shake and here comes the whole 'Hundering Therd'! LOL
I agree with above, no horse can withstand the sound of a bucket of feed shaking :)
I'm blessed with my gelding, he is on about 20 acres and finds his way to the gate no later than 3pm every day. Loves the idea of getting out in the morning, once out in the wind and rain for a few hours he then loves the idea of dinner,a warm bed and a good helping of haylage.
I don't call him often, he knows my jeep and can see me coming in from the main road, without fail by the time I'm out of the jeep he is at the gate waiting.
Sometimes in the winter when I feed, after I start throwing out the flakes, I will yell (ok--screech), "Pony, pony, ponies." They are usually already on their way.
Two summers ago, packed in to Eagle Cap Wilderness, all the horses were grazing in a meadow. It was marshy in some areas and we didn't want to slop through it. So I tried the screech thing. Guess what? Mine came and brought the others with them! It helped that we fed beet pulp when they were high-lined.