Marshall (1942) Chlorophonia occipitalis (Heard by MH at Los Esesmites) V de Santa Ana Common in the heaviest, densest, greenest forest trees on the North slope of Cano de los Naranjos where feeding in high or medium high foliage but could get close to them on steep hills. In groups of 3 or more per tree. Call remindful of Sayornis say a plaintive long pure whistle, but in this species is lower & fuller & rounder tone. But very pathetic and slightly inflected down. Feed among light green branches & foliage & blend very well. Hildebrand camped out on Los Esesmites & heard these calls, probably in early am or evening. I don't recall having heard them although I was there for the "dawn chorus" of Bram Robins.