61 NW Tonala' April 8 Differences in general behavior between humilis and nigricaudatus. The song is different, however, I have decided that the most commonly given song of humilis is a rapid Pe-coo, Pe-coo, Pe-coo - both notes of about equal value - although the latter is longer. Also heard a good deal was a triplet pe-tee-co pe-tree-co, etc. We noted a difference in getting the head back thru the neck - in humilis the neck seems narrower. The plumage of humilis is more worn - possibly from more frequent contact with bare branches & thorny vegetation. Tonals apparently less well developed than those of recent nigricaudatus we have examined. No evidence of chiapensis today - we were well, beyond its limited range. Probably our locality 5.4 mi. NW is at the NW boundary of [illegible] the range of chiapensis. April 9 Drove out NW to Rio Tiltipee (erroneously called the Rio Amatillo in previous notes and on the map). Just to the left of the road we stopped along the river and spent all day observing chiapensis and humilis (see large map). Found pair of humilis about a nest placed in a dead bull-horn acacia about 17 feet up (Pool 13-1 color). Carrying nesting material in the morning but not in the afternoon.