The sirens started it. 
The big coyote close by in our neighbor's vineyard immediately chimed in, adding some local color to this afternoon's visit by some lovely people from Michigan.  "Creeps me out," one said, hastily taking cover. 
I should have mentioned that the resident coyotes never harm anything bigger than a jackrabbit, of which Rodeno Vineyards has a plethora.  They didn't even hassle our free range Araucana chickens. The neighbor's dog did, however, so I'm secretly hoping the coyote next door will find that little dog to its liking.