You're right, coyotes can howl any time during the day, but I can only count on one hand the times I've heard a coyote bark or howl while it's been light out, at least that's just how it is on my farm. They're so much more active at dusk, dawn, and throughout the night that that's the times when you'll hear them the most. If I use my howler I don't worry too much about spooking birds the other way because I howl well before a bird even thinks about leaving a tree, which gives him plenty of time to settle down. Also, birds have coyotes and other predators running under their trees and howling and making racket throughout the night, and I think they get somewhat accustomed to it. That morning I told you I heard the coyote howling, I decided to head in that direction about 2 hours after sunrise to try and strike up a bird and I saw tracks from a couple of hens right in the exact area where the coyote was.
One more thing, I don't set up in the exact location I howl from, or crow or hoot from for that matter. I like to move at least 50 or more yards from the spot, but that all depends on the terrain and how close you are to birds. I have the Primos Lil Dog and it seams to work fine for what I need it to do. Hope this helps!
