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(?),                  Nov. 21, 1960 II  78

  These Booms must have been hostile. Probably at least moderate intensity. Perhaps escape predominant???
  Since then we have heard one or more of the birds of the firsts clutch utter Booms almost every time we have chased the other birds.
  As far as I can tell, the Booms are not accompanied by any special ritualized movements or postures. Apparently uttered with bill closed.
  I think that I probably heard Booms uttered by some of the birds of the first clutch at least 1 month before November 2, but I can't be absolutely sure about this.

 (?)                   November 22, 1960
                       Barro Colorado

  We tested the chicks of the 3rd clutch again this afternoon, ca. 1:20 p.m. One was silent throughout, as usual. The other gave a sort of ruffled, irregular Squawk when caught. Then began to utter very faint clucks (from very to clucks is underlined) when passive in hand. With bill closed, throat moving in and out. These chicks developed gradually - from the sound of heart beats.  Obviously the first stage of the Cluck pattern as a whole.
  It is possible that these birds have been somewhat retarded in developing or, at least, showing the Cluck pattern because they are so shy. It is my impression that escape tends to inhibit clucks.
  The birds of the (?) clutch still utter both 00 notes and clucks when I approach their cage.