I have always felt that the best success on calling coyotes is to first locate the coyote if at all possible.
There are so many good 'locating calls' anymore that not having one and learning how to use it seems to be at a disadvantage.
Sirens have also used as locators.
Works good until you get into an area thats been exploited hard and the coyotes go silent.
And they WILL go silent when pressured hard.
I worked a pasture once in late summer/early fall about the time the pups are just starting to get a little vocal. The owner was getting ready to drop some goofy early fall calvers and wanted the dogs gone. I knew there was a litter in there. It SHOULD have been a simple matter of going in, getting the pups to talk just a bit, than going in and cleaning em up.
Well, I DID get the pups to answer me. Than I heard three distinct barks from another coulee bottom a quarter mile away, and all was quiet. I couldnt get a coyote to answer me in there (and they never left) again.
Momma (im guessing) was on to that game, and she reprimanded those pups with just a few barks.
Now fast forward to when those pups reached adulthood. They were raised by a female that was probably not into talking to much, and they got reprimanded probably more than one time for being vocal. What are the odds those coyotes grew up to be highly vocal?
Passing on experiential learning is something that has been fairly well documented in coyotes.