THE BITTERN 341 



made by the male alone, or as answering calls by both sexes. In 

 earlier days it was believed that they were produced by thrusting the 

 beak under wa,ter and then expelling air through the mouth, or, accord- 

 ing to another version, by thrusting the beak into a reed a strange 

 achievement having regard to the bore of the reed and the thickness 

 of the beak. But even then there were dissentients, for Montagu 

 insisted that the "boom" was usually uttered while the bird was high 

 in the air ! To-day we know that all these interpretations were wrong, 

 for this strangely resonant cry, which can be heard a mile off, is made by 

 the bird when the beak is closed and pointed skywards. The sounds, 

 which are generally compared to the bellowing of a bull, are preceded 

 by certain throbbings in the throat, apparently inspirations of air, 

 which is then suddenly expelled while the beak is apparently closed. 

 So far as we know to the contrary, they are made by the male only, 

 but it is possible that the female also booms. Possible, because even 

 in the male the syrinx displays no modification, which can be regarded 

 as explaining the volume of sound emitted. But in this respect the 

 bittern does not differ from the ostrich and the cassowary, in both of 

 which the males emit resonant drumming or booming sounds, though 

 lacking even a syrinx. 



The bittern has at least one other note, syllabled kduw, no doubt 

 an alarm-note. It was heard from a bird, flushed, " apparently near 

 the nest," while it circled in the air. Its note was answered by the 

 boom of its mate hidden in the reed-beds. 1 The note of the young 

 will be referred to below. 



As touching the coloration. There can be no question but that 

 this is pre-eminently of the " protective resemblance " or " concealing" 

 (procryptic) type. Yet it is significant to notice that it differs in some 

 striking particulars from the nearly related American-bittern (Botaurus 

 lentiginosus). Not only is " the common " bittern (B. stellaris) a more 

 brightly hued bird, but the remiges are conspicuously barred, while in 

 the American bird which is also reckoned a British species these 



1 British Birds [magazine], i. 332. 

 VOL. IV. 2 X 



