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(?) major, (underlined) Apr.20, 1960, I    24

  They reacted to my voice, all tones & lengths of notes, in (?)the same way as on April 17th, but much less vigorously. They did
nothing more than Tsh's, and not many of these, when I spoke to them normally in my ordinary voice. I had to utter "ooooooo" 
sounds to provoke ruffling, preening, and gaping & (?).
  Again M reacted more vigorously than Hrr - but not very much more so.
  Tsh's are obviously the lowest intensity form of this reaction. Preening (& ruffling, which seems to be correlated with preening, although by no means all preening is accompanied by ruffling)seems to be moderate intensity. Gaping & (?) is obviously high intensity.
  Both birds have white chins and throats. This white is often quite conspicuous when they gape & (?). The insides of their mouths are rather dull pink or flesh-colored. This is not very conspicuous when they gape and (?).
  I thought that both birds (especially M) showed a definite tendency to peek at spots on the ground or small (?) more frequently than usual when I uttered "oooooooo" sounds. When they were performing fairly vigorous preening and/or gaping & (?) patterns.
  M showed a definite tendency to move away from me and toward David when I uttered "oooooooo" sounds.
  As a result of tonight's tests, I am sure that it is the "ooooooooo" sounds alone which provide the strongest stimuli. The consonants 
preceding "ooooooooo" seem to be quite irrelevant - and so does the pitch of the "ooooooooo"s, but the difference does not appear to be great.
  There seems to be no doubt that M performs gaping & (?)