HEARING — FIELDWORK AND EXPERIMENTS «I 



tiny Goldcrest, or the loud bang of a gun or a stone hitting 

 a wooden fence. 



The songs of birds are mainly for the purpose of proclaim- 

 ing and maintaining territory, and are not, as so many 

 sentimentalists think, uttered in order to charm hen birds 

 by their beauty. They are certainly not for the purpose of 

 pleasing us, however lovely they may be. But the song of 

 a cock bird will be heard by his mate and so assist in 

 stimulating the activity of the sex hormones which bring 

 about mating and egg-laying — as any canary breeder should 

 know. 



There seems to me to be little point in trying to devise 

 experiments to show that birds have acute hearing in the 

 wild state — particularly in the case of what are popularly 

 known as song-birds — because their auditory acuity is well 

 established. At the same time, it is worth while to consider 

 one or two other aspects of hearing in birds. 



I once had the good fortune to hand-rear a cuckoo from 

 the time it was a few days old until it migrated, and I was 

 struck by the great sensitivity of this bird's hearing powers. 

 While it was still being largely fed by hand, I used meal- 

 worms for the insect portion of its diet. These beetle larvae 

 (for that is what they are) were kept in a tin near the cage 

 in which the cuckoo was housed. I was very intrigued to 

 find that when I picked up the tin the bird would increase 

 the frequency and intensity of its hunger-calls. Though it 

 would have been tempting to attribute this to intelligence, 

 much experience in rearing young animals had taught me 

 that most — but not all — behaviour of this kind is due to the 

 high development of one sense or another. That I was right 

 was proved to me when this cuckoo was a little older and 

 had, at intervals, some measure of freedom within the room 

 where it was kept. I noticed that when hopping about it 

 would move towards the tin of mealworms and cock its 

 head sideways in what I can only term an attitude of listen- 

 ing. It would go right up to the tin and would peck at it. 

 When the bird was old enough to feed itself, and the flat 

 tin containing the mealworms was opened, the mealworms 

 would immediately be attacked and eaten — too many of 

 them, if I did not intervene. 



