Pup distress — the frantic screaming of a coyote pup in mortal danger — is the single most universal trigger in predator calling, working year-round because it fires two simultaneous motivational cylinders: parental protection (hunger season) and territorial aggression (any coyote can't allow a pup to be killed in its range without responding). Al Morris documented this as a "mandatory stand-ender" — played as the final sound on every stand, regardless of what came before, because it generates responses even when everything else failed.
Use pup distress as the third stage of a calling sequence, after prey distress has run its course. After the first shot in a multi-coyote setup, immediately switch to pup distress — the gunshot simulates the attacker killing something; pup distress tells any approaching coyotes that the pup fight is still happening. Always end every stand with pup distress 3 (or equivalent premium recording). The female protective response does not distinguish time of year — a bred female in January is already conditioned to guard pups; the sound fires the reflex regardless. In denning/pup-rearing season (April-August), switch the sequence emphasis to pup vocalizations as the primary trigger, not a closer. The parental instinct to protect is actually stronger than the hunger drive in most adults.
The conventional wisdom is that pup distress only works in spring and summer when actual pups exist. Al Morris and Tony Tebbe both document pup distress triggering responses in January with snow on the ground. A bred female in late winter is already biologically primed for pup defense — the hormonal conditioning precedes the birth. The trigger doesn't know what month it is.