654 THE POPULAR SCIENCE MONTHLY. 



more highly developed form of the common vertebrate sensibility. 

 When we reflect upon the purely physical and physiological basis 

 which, as Helmholtz has taught us, underlies the musical intervals and 

 the distinctions of harmony and discord, there is certainly no reason 

 why they should not be perceived by all the higher animals alike, in a 

 greater or less degree. 



Considering, therefore, the evident susceptibility of birds to the 

 simpler pleasures of music, and the interest which they show in it even 

 apart from their domestic relations, there is no a priori difficulty in 

 accepting the belief that their powers of song may have been developed 

 by mutual selection, provided no adverse argument can be shown 

 against the probability of such selection ever proving a cause of spe- 

 cific variation. To this last question, the question so ably raised by 

 Mr. "Wallace, I shall return on a later page. 



Passing on to sight, we have first to observe the effects of mere 

 light or brilliancy upon birds, apart from special effects of color or 

 form. Now, birds certainly share with insects and many other crea- 

 tures the common fascination for bright lights. " Owls and night-jars 

 have been known to flutter against the window of a lighted room in 

 the small hours." * In the tropics, where windows are more constantly 

 left open, birds frequently fly into houses, attracted by a lamp or can- 

 dle. The reflected light of a mirror is employed to draw down larks. 

 Magpies delight in secreting diamonds, gold, silver, and other shiny 

 objects. The bower-birds use shells, polished pebbles, and like brilliant 

 odds and ends in the construction of their bowers. So, too, metallic 

 iridescence occurs frequently in the feathers of beautiful species, nota- 

 bly in the humming-birds, sun-birds, peacocks, and other flower-feed- 

 ing or fruit-eating classes. But even the far less brilliant crows, gulls, 

 ducks, and doves show exquisitely burnished gloss or luster on their 

 coats, often specialized upon particular portions of the plumage, and 

 apparently betraying the action of sexual selection. 



Of the love for color shown by birds, I have already treated so 

 fully elsewhere, that it will suffice here briefly to recapitulate the main 

 facts. The universality of bright hues in the fruits which depend 

 upon birds for the dispersion of their seeds clearly shows that fruit- 

 eating species are attracted by red, blue, purple, and yellow ; just as 

 the analogous case of insect-fertilized flowers shows the preference of 

 bees and butterflies for similar tints. Mr. Darwin has collected several 

 instances of interest displayed by birds in colored objects-, and of the 

 attractiveness which color evidently possesses in their eyes. Of these, 

 the most remarkable cases are those of the bower-birds' and the hum^ 

 ming-birds' nests. And the constant occurrence of very brilliant hues 

 among flower-feeding species, such as humming-birds, sun-birds, lories, 

 and barbets, or among fruit-eaters, such as toucans, fruit-pigeons, birds- 



* This, with several other instances, I take from an interesting article on " The Senses 

 of the Lower Animals," in the "Quarterly Journal of Science" for July, 1878. 



