First eggs..and are they hiding some?

Hi all, first time with chickens here. All 27 of my girls are 5 and a half months old, White Leghorns, Australorps, Single Comb Browns, Araucanas, and Silver Laced Hamburgs. Last Monday I found their first egg, a medium sized white one, on the floor of the coop. The next morning I found another white egg on the floor again, slightly bigger than the one from the day before so I gave them access to their nest boxes for the first time. Two days passed with no eggs, then one tiny white egg (smaller than a golf ball) on Thursday and Friday, this time in the nest boxes. Now 3 more days have gone by with nothing again. I know they are just starting to lay, and we are in the midst of the shortest days of the year but is this typical of how they start to lay? They also have free range of 10 acres of field and woods so naturally I'm concerned they may be laying elsewhere.

 

Thanks sourland, I've had two golf balls in each nest since I gave them access to it last week. Scoured my property a few times already, the barn, etc. I'll look some more later. Could they be hiding them? Or is this what I should expect from brand-new layers at the end of December...