Marshall, 1942 Nyctedon obscurus Los Esmeriles March 23 ? 2153 taken early foggy am. on 2nd growth hill where owl set up in dense low trees & large poplirs around. This bird didn't come n but gave several loud stean-whistle alarm notes (higher limit thn.) then started singing again. Saw it fluttering in young trees. This settled a long ? we that this singer was nightengal, thns- but song has some notes qual to M. unicolor but entirely different pattern- very swift succession notes rich in overtones but harsh combinations like creaky wheel turning round & round. A song lasts about 8 or 10 sec. High overtones seem about every second & start again while low ones are getting under way, hence "revolving" nature. Heard every day here early am & evening & at intervals during day, more regularly when cldy. A ? in every canyon below cloud forest where dense brushy trees (2nd growth). Never 2 together except today (the other ? came to the owl for just an instnt.) & was probably the one from next ravine. This is the hardest bird of any to get-unbelievably away. One seen yesterday - flew across ravine. Not nearly as common as M.unicolor. Spread out on breeding tour.