INTRODUCTION 25 



land and England feels confident in ruling out the possibility of a sense of smell. 

 Nevertheless, I have hundreds of times decoyed ducks and geese directly up wind 

 where they had plenty of time to detect my presence, without their showing any sus- 

 picion, so that one becomes very skeptical that what has been described as a sense of 

 smell in birds is really analogous to what we see in mammals. It has been suggested 

 with reason that birds are provided with some more or less "occult" power of finding 

 food; and the extraordinary ease with which diving ducks discover hidden water- 

 plants seems to rule out a mere happy-go-lucky trial-and-error search. 



Some evidence for and against a sense of smell in birds has been summed up by 

 Mr. J. H. Gurney in the Ibis for 1922. 



VOICE 



The various call-notes of water-fowl are among the most interesting of all sounds. 

 A few, as the "south south southerly" song of the Long-tailed Duck, or Old-squaw, 

 the whistle of the Widgeon, and some of the notes of Teal, are really musical, but 

 for the most part they form a great variety of sound with little musical merit. 

 A large raft of Mallards, Teals, Pintails, and Widgeons, especially when feeding 

 at night, gives off a confused volume of sounds, mostly rapid chatterings, jabberings, 

 coarse low, and squeaky high-pitched quacks, with now and then sharp whistles. 

 In the spring, male ducks have special courtship notes, and these are very curious 

 and entirely unducklike in character, such as the catlike "meeow" of the male Red- 

 head, and the rarely heard dovelike coo of the Greater Scaup, audible only a few 

 yards away. These notes are very often intimately associated with display attitudes. 



Diving ducks of almost all kinds are much quieter than the surface-feeders, and 

 most ducks are rather quiet while flying. The Tree Ducks, which are obviously noc- 

 turnal, are exactly opposite, for they continually keep up the most amazing whistles 

 while on the wing, and they are very silent on the ground or water. 



On the whole, the remarkable boxlike bony pouch situated near the bifurcation of 

 the trachea in the males of most ducks seems to act as a voice-stopper and tones 

 down the quack to a reedlike note or whistle. The differentiation of the voice is one 

 of the earliest signs of sex in Mallard Ducks, and the "quack" when once heard in- 

 variably means a female. There is, however, a period at which the voice is half male 

 and half female, when it is extremely puzzling to make out the sex. Young ducks in 

 down make a variety of small peeping sounds. 



Embryo Mallards show a swelling of the windpipe in both sexes, which gradually 

 disappears in females, so that some time after hatching it is not noticeable in that 

 sex. 



Those species which do not have a tracheal box have some other curious secondary 

 sex character, like the tracheal air-sac of the Ruddy, the subgular pouch of the Musk 

 Duck, or the oesophageal dilatation in the Black-headed Duck (Heteronetta). 



