262 U. S. NATIONAL MUSEUM BULLETIN 211 



2-note phrases between songs, and if one considered these to be separate 

 songs, there would be many 1- or 2-note songs. 



"The pitch of the songs varies from F" to A'" '. The range in pitch 

 of single songs varies from 1 tone to 6 tones, or an octave. The 

 average range is 3% tones. It is interesting to note that the only record 

 I have that is definitely the song of a female bird has a range of only 

 1 tone. 



"In time, songs vary from % to 2% seconds. Though all of the notes 

 are rather short, there is often considerable variation in the lengths 

 of the notes of a song, so that, though the song has a rhythm, it is 

 not often an even rhythm." 



The bird not infrequently sings while on the wing in early spring, 

 and occasionally in August. 



Ralph Hoffmann (1904) says: "The female during the mating season 

 whistles two or three notes similar to the male's," and Tilford Moore 

 (MS.) has heard a female sing "short, finished songs." Both sexes 

 give a long grating chatter which often seems to indicate anxiety, and 

 this is sometimes incorporated into the song. 



The period of singing is short. The bird arrives on its breeding 

 ground in full song and continues to sing all day long during the 

 mating and nest-building stage of the cycle, but by the end of June 

 there is a noticeable falling off in the singing, and during the molt the 

 males are almost silent. Then, about mid-August, a fortnight before 

 they leave, the males sing freely again, chiefly in the early morning. 



Brand (1938) gives the approximate mean vibration frequency of 

 the Baltimore's voice as 2,500 cycles per second, slightly below that 

 of the robin and not far from that of the bluebird. 



Enemies. — Elon Howard Eaton (1914) speaks thus of the Balti- 

 more oriole's enemies: "In spite of the skilful placing of the oriole's 

 nest, it is frequently visited by plunderers. I have seen crows on 

 several occasions succeed in getting young birds from the nest and 

 the home of the Screech owl very often shows that the young orioles 

 have been taken and fed to the owlets. Red squirrels also descend 

 to the nest to get the eggs and young birds, and I have seen the gray 

 squirrels do this on one or two occasions. Generally, however, the 

 young are reared successfully and I am inclined to think that dangers 

 in migration and severe weather are the principal checks to the in- 

 crease of this species." Referring to the incessant calling of the young 

 birds, he says that from their notes the young "are unquestionably 

 located by many predaceous animals and thereby destroyed." 



Forbush (1927) tells of a case in which nine bronzed grackles 

 attacked a pair of orioles, "but after two minutes of swift action the 

 Grackles retired from the combat, leaving the 'orioles' the victors." 

 John T. S. Hunn (1926) reports "An Oriole Tragedy." The male 



