There was no siren this time — sirens are what often sets off coyote howling in the city, where they usually begin in tandem or pretty close together. This howling reflects their unity as a family, and possibly territorial separateness from any neighboring coyotes. For more about oral communication, see my post on Voicings.
But this time, it was SHE who vocalized alone: she was calling out to him repeatedly. Rather than answering in-kind and right-off, he apparently responded by actually coming. Then, once she was in his line-of-vision, he began his high-pitched, pup-like locutions, and then her calls morphed into the same type of little “hello there” whines and squeals. These are greetings.
These two coyotes are an old, mated pair. Their evening rendezvous, which this is, although joyous in its own way, was more a confirmation of each coyote’s status towards each other. The male is the dominant fellow in many ways, and you can see this when they finally come together: she crouches down and lets him stand over her: it’s their little ritual. But note that she is the one who did the calling. A more “conversational” back-and-forth communication over the distance can be heard here.
After the meeting/greeting they both went off hunting separately, but sticking close by to each other. Coyotes are social and enjoy each others’ company.
Coyote Yipps 
Dec 27, 2018 @ 16:57:49
I love this. Thank you!!
Dec 27, 2018 @ 22:18:19
Thanks for your illuminating posts. This helps explain similar vocalizations I often hear at night in Pacifica.