I used to get out and be in place before first light, and then noticed I did not get as many coyotes as I did later in the day, say after the sun was up.
I concluded that a coyotes night vision is far superior to mine, and many times, while I was walking to a stand in the dark, they were watching me walk in and sit down. No way they are coming to my call.
For the past 20 years or so, I get out there about 8-8:30am, and I do well. My theory is that by mid-morning, they have found a place to nap for the day and that makes it easier for me to cover ground without being seen. Then my call is like a 'come to breakfast' invitation.
I seem to call as many during mid-day as I do late afternoon.