Which of Harners books was it? In, The Jívaro: People of the Sacred Waterfalls, he writes a brief account of the uprising in which the Spanish colonists were massacred. The people he called Jivaro are now called by their own word for themselves, the Shuar. Macas is, and has been for 85 or so years, the capitol of the Ecuadorian state of Morona-Santiago. Most of its inhabitants are either Shuar, or immigrants from the nearby province of Azuay, in the Ecuadorian Sierra, who mostly arrived after 1950. I don't think any claim to be descendants of the colony that was massacred, but I'll look into it and post again.

Edit: The University of Cuenca has just begun to digitize the archives of CREA, the Centro de Reconversión Económica de Azuay, Cañar y Morona Santiago. That organization was the driving force in the mid 20th century development of Macas. So, the primary sources available are about to expand immensely.