2017 started with first sighting on March 4 and second sighting March 11. I finally heard vocalizing and my third sighting on Tuesday March 21. Today, March 26 I am only up to four birds but i expect numbers to increase almost daily from now on as long as weather stays nice, which is the forecast.  

Its is obvious that the first arrivals do not always stay around and that they may be birds passing through but at very least they don't spend a lot of time at their colony.  The last several seasons I have been lucky to see the first bird. After the first sighting several days passed until the next sighting. It is easy to see how the term scout came to be used to refer to the first Martin's seen.  Since they are not seen every day and don't spend night an explanation is that they check things out then return to bring in others.  

  Even though the term scout is still used it is not believed that they perform a leadership role.  

My Martin's are now spending the nights but with three here since Tuesday only one was seen going in at night.  The others are either zipping in unnoticed or staying elsewhere.  I think elsewhere since I have watched closely each evening.