52 SEXUAL SELECTION': BIRDS. [Part IL 



nothing is more common than for animals to take pleasure 

 in practising whatever instinct they follow at other times 

 for some real good. IIow often do we see birds which fly 

 easily, gliding and sailing through the air obviously for 

 pleasure ! The cat plays with the captured mouse, and 

 the cormorant with the captured fish. The Aveaver-bird 

 (Ploceus), when confined in a cage, amuses itself by neat- 

 ly weaving blades of grass between the wires of its cage. 

 Birds which habitually fight during the breeding-season 

 are generally ready to fight at all times ; and the males of 

 the capercailzie sometimes hold their halzens or leks at the 

 usual place of assemblage during the autumn." Hence it 

 is not at all surprising that male birds should continue 

 singing for theii* own amusement after the season for 

 courtship is over. 



Singing is to a certain extent, as shown in a previous 

 chapter, an art, and is much improved by practice. Birds 

 can be taught various tunes, and even the unmelodioiis 

 sparrow has learned to sing like a linnet. They acquire 

 the song of their foster-parents " and sometimes that of 

 their neighbors." All the common songsters belong to 

 the Order of Insessores, and their vocal organs are much 

 more complex than those of most other birds ; yet it is a 

 singular fact that some of the Insessores, such as ravens, 

 crows, and magpies, possess the proper apparatus," though 

 they never sing and do not naturally modulate their voices 

 to any great extent. Hunter asserts^* that with the true 

 songsters the muscles of the larynx are stronger in the 



" L. Lloyd, ' Game-Birds of Sweden,' 1867, p. 25. 



*' Barrington, ibid. p. 264. Bechstein, ibid. s. 5. 



** Durcau de la Malle gives a curious instance (' Annales des Sc. Nat.' 

 3d scries, Zoolog. torn. x. p. 118) of some wild blackbirds in his garden 

 in Paris which naturally learned from a caged bird a republican air. 



*' Bishop, in ' Todd's Cyclop, of Anat. and Phys.' vol. iv. p. 1496. 



*' As stated by Barrington Id ' Philosoph. Transact.' 1773, p. 262. 



