Humilei - chiapensis 65 Rio Tiltepec April 9 in several spots in the study area but the strata difference is about 100% effective as humilei almost never descends to the ground while 95% of foraging of the thryothorus is among dead leaves on the ground. The Thryothorus were singing continuously in the morning - Probably at least 4 pair in the study area and perhaps more. Today's study shows that both humilei and chiapensis can line side by side. It also shows partial ecological separation in place occurrence although there was a good deal of overlap in are presented. Humilei was 3x as common as chiapensis and I think it significant that one pair of chiapensis was localized in the area along the largest group of trees - the anates- with adjacent thick vines. This was a situation similar to Tonala' where large trees are present in meadows and where the hedge rows are fairly narrow but consist of large trees a thick vines. Apparently in Tonala' area proper there is no available habitat for humilei. Certain, an study today shows that humilei can occupy the same type of area as does chiapensis - although perhaps, the smaller trees & thicker brushy areas are required also. Chiapensis is more restricted ecologically - it does not forage through small trees or on vertical trunks to anywhere near the extent that humilei does. The presence of large trees seems to be necessary for