LLW04 1767 Aimophila mystacalis August 16 16.5 mi. SW. Matatlan, Oaxaca, Mexico Km. 616 on Pan Am. Hwy. Area is Acacia + tree with spines on trunk - dominated hillsides. In places trees form almost to completely closed canopy at 10-15 feet up. Shrub layer well represented at 4-8 feet, but most pronounced at places where tree cover reduced. Herb layer of grass + weeds up to 2-3 feet tall. Much of grass grazed by livestock so just carpet up to 1-2 inches tall. Along fence bordering maguey fields are Acacias + some perennials growing to 4-5 feet. Pair #2 restricts most of their activities to S. side of road. Where come to a side equal dust as 2nd joins 1st. This usually is followed by duet of pair 3 which flies up into Acacia, maguey or onto fence post. Heard pair 2-3, 2-9, 2-3-5 counter-duet. Have not heard 2 pairs start duet at same time so one is undoubtedly stimulated to duet by duet of 1st. Have twice seen pair as come together for duet & at least one bird is wing flicking at start, but only for 2-5 sec + for less than first half of the duet. Not sure if both birds wing flick. Even though have counter-dueting by adjacent pairs they do not come together, but remain at least 30+ yds apart. Birds do move closer together or along line parallel to other pair during duetting. Have not seen pairs duet - even when counter-dueting - without changing perches. Always one bird follows the 2nd & chatter duet starts when 2nd arrives. Duet seems to function as territorial announcement by resident pair, but has not been completely changed from reunion performance. Both members of pair apparently contribute to the duet, but as in bunwacas it sounds as if one sex is more elaborate.