26 



CHIMNEY SWIFT 



FIG. 9. 



Short, 

 widely gap- 

 ing bill of 



Swift. 



FIG. 10. 



Long, probe-like bill 

 of Hummingbird. 



build its nest. It would be quite impossible for 

 an ordinary bird to fasten a wall-pocket of twigs 

 to a .perpendicular chimney, but the Swift is pro- 

 vided with a sali- 

 vary glue that de- 

 fies anything but 

 heavy rain, actu- 

 ally having been 

 known to hold firm 

 when the brick to 

 which it had glued the nest was broken away. 

 Nature selects beneficial qualities rigorously, or 

 rather the struggle for life is so intense that only 

 the best fitted survive to hand down their charac- 

 ters to their race ; but Nature makes no meaning- 

 less display. Eggs are colored because they are 

 exposed to enemies, and those whose colors best 

 disguise them are most likely to escape the eyes 

 of enemies ; but let the eggs be laid in a tree 

 trunk, a hole in the ground, or otherwise out of 

 sight, and as a general rule they will be white. 

 There is no force at work to eliminate the white 

 ones. So we see this negative adaptation in the 

 eggs which the Swift secretes in a chimney, 

 they are pure white. 



It would be exceedingly interesting to watch 

 the Swifts at the nest ; and while their habits or- 

 dinarily render this impracticable, Mr. Otto Wid- 

 mann, the original and philosophical student of 

 birds, has shown how it may be done. He accom- 



