Any distress call will work. Coyotes don't reason and if they hear something dying, they come to it.
The exception is that later in the season, they start thinking more about breeding and less about food. Coyote sounds work better then. a challenge howl or high pitched female howl works great from mid feb on.
TRUE, any distress call can work, and true they don't reason, BUT they don't and won't
alwayscome to a call of any kind. Sometimes, they just wont'/don't come to a call.
There is no exception, they have to eat all year. A couple of reasons that later season tactics/sounds need to change. #1) later in the season they have been educated to the point where they simply won't come to just any distress sound. If they've been shot at after responding, they do tend to learn from that experience, #2) howls work better during breeding season because howling is how they communicate. They are territirial and will defend their home territory against nomade coyotes, plus they are looking for mates, hence the female invitational howl works well.
If a guy could find coyotes late in the season that have not been called for a year or more, distress calls would be the first calls to use, no matter the time of year. However, howls can and will work any time of the year also, BUT they work better during mating and denning season!