Changelings ebb and flow,
as populations go.

Changeling Queen’s can produce several hundred eggs within a year, and several thousand before they cease production.  However, if their hives are discovered they are often destroyed as ponies have come to loathe changelingkind, and have since their outset when changelings were much, MUCH different creatures.

There is always the possibility of changelings achieving a much greater splendor than they have or have had in the past.  There have not as of yet been grand extravagant changeling cities or societies though, due to their natures and the situation of their social and physical evolutions, situations of fear, flight and famine.