when the Back Bay Basin at Boston was a tidal estuary, 
Golden-eyes frequented it much more than they do now, 
and one could often hear from the city streets the whistle 
of their wings as they flew out at sunset or back in the early 
morning. The wing music, loud as the birds pass at close 
range, grows rapidly fainter, but can often be heard until 
the birds almost disappear in the distance. I have noticed 
a considerable difference in the loudness of this wing music 
at different times and have endeavored to separate the tones 
of male, female and young, and the difference in the season. 
Sometimes the whistling is very loud, at other times it is 
almost absent. As the birds are nearly always associated 
in groups of different sexes and ages, and as the conditions 
of audibility vary with the wind and weather, I have been 
unable to come to definite conclusions, but I am inclined to 
believe that the wing music of the males is louder than that 
of the females and that it is heard at its best in the spring. 
Mahoff * has made an interesting study of the wing music 
of the European Golden-eye, which bird differs from the 
American sub-species only in being slightly smaller. He 
has recorded a number of careful observations of the “flight- 
tone” in this species and finds that the whistling is loudest 
in adult males. In adult females and young males the 
whistling is either absent or only half as loud as in the 
adult males, and he records one case of a male in eclipse 
plumage where the sounds were faint like those of the 
female. The mechanism of this instrumental music he 
attributes mainly to the narrowing of the barbs at the ends 
of the first two primaries, a condition that is found only 
in the males. He believes that this wing music adds to the 
community life of Golden-eyes, who are thus able to signal 
and keep in touch with each other, and that it plays no role 
in courtship. 
Can it not be the case that this whistling was originally 
developed in courtship, as suggested by the secondary sex¬ 
ual specialization of the wings, and that it is now used, as 
Mahoff points out, for signalling? 
* “Zum Schwingengerausch der Schelle'ute (Glaucionetta c. Clangula L.),” 
published in “Verhandlungen der Ornithologischen Gessellschaft in Bayern,” 
XIII, Heft. 4, Nov. 25, 1919. 
9 
