MIND AND MEMORY OF BIRDS. 19 



and is modifying its bill from the ancestral 

 wedge shape of the woodpecker's beak, to 

 that of the slender, curved mandibles belong- 

 ing to the thrushes and the meadow-lark. 



The house -wren rarely builds its nest in the 

 crevices of cliffs or in the hollows of logs and 

 trees, as it once did. It seeks the habitations 

 of man and is modifying its nest architecture 

 to suit the new situation. 



The sap-sucker (yellow-bellied woodpecker) 

 is losing the power to protrude its tongue far 

 beyond the end of its bill, a very striking 

 modification going on apace with its depart- 

 ure from the true woodpecker habit of feed- 

 ing. Some of the woodpecker species, the 

 hairy woodpecker, for instance, can thrust 

 forward the tongue more than two inches 

 beyond the point of the bill, while the sap- 

 sucker can reach scarcely one-third of an 

 inch. 



In the case of wading birds, those species 

 which have chosen to live near small streams 

 have shorter legs and neck than species 

 which prefer larger streams, lakes or sea- 

 borders, and, taking the little green heron as 

 an example, as our streams diminish in vol- 

 ume year by year, the bird modifies its habit 

 in accordance with necessity, and in my 

 mind there is no doubt that its legs and neck 

 will be affected, in the course of a compara- 

 tively short period, to a noticeable degree. 



The blue- jay is either a corvine croaker 

 passing into the song-bird's estate, or a song- 

 bird whose natural desire for singing is fading 

 away, leaving it to relapse into the crow's 

 unmusical condition; for its voice has a strain 

 of genuine melody in it mixed up, almost 

 comically, with the harsh discords of the true 

 crow-caw. 



