Empty Bird Box?

Earlier this month Jeanette saw Black-capped Chickadees entering this bird house with nesting material.  We haven’t seen any activity recently, so yesterday I decided to check the box to see how much of a nest they had started. When I opened the box I was startled by a fleeing bird and I discovered a completed nest of grass and moss, and nestled in the bottom were 5 little eggs! My next question was - where are we in the process.  I was able to go back in my records and find the date of Jeanette’s observation as May 2.  I knew from past research that nest construction takes 3 or 4 days, and incubation takes from 10 to 13 days, but how many days for egg laying?  It’s been an answer I haven’t been able to find in any of my books, but today I found in on the internet, of course.  Cornell’s site, All About Birds says; “Virtually all songbirds lay one egg per day, usually in the early morning, until the clutch is complete.” Constructing a time line, the nest would have been finished by the 6^th at the latest, egg laying completed around the 10^th, so we are now in the incubation period.  We will be watching closely for the more obvious signs of the adults bringing insects to the peeping sounds in the box.