Females are sneaky going to and from the nest.
Our recommendation for incubation is systematic sweeping but be aware of far away flushes to mark the general area. Males are generally quicker and less cautious when approaching the nest. If the female flies far away while observing her with food, hold your ground because she is probably trying to throw you off the trail and will return. He becomes very agitated, flying near you and chipping loudly if you attempt to approach an area where there is likely to be a nest. It's better to be patient and wait for the male to leave the area, so you have a better chance at catching the female unaware.