It took a few hours of inching my way closer as the bird got used to me. They will chirp when unhappy. If they raise there tail feathers when you move then be still longer and try to inch a little more. They always come back very soon when setting on eggs.
The Killdeer will run a good ways from the nest and act like it has a broken wing to draw preditors away from the eggs then fly away at there approach and circle back to nest.