390 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loa 



On the nth day the bird begms to ruffle its plumage, a type of move- 

 ment not indulged in hitherto. The feathers, now all out of the 

 sheaths, become darker, more pronouncedly blackish and less grayish 

 due to the increased area of their newh^ freed portions. The ventral 

 edge of the bend of the wing is white, the alula is black, and the under 

 primary coverts are black with white bars; the feathers of the breast 

 and sides of the abdomen are hght buff with a black subterminal and 

 a broad buff terminal bar; the feathers of the midabdomen and thighs 

 are paler. On the 12th day the rectrices show the contrasting white 

 tips very markedly because of the growth of the dark proximal portion 

 of the feathers. By this day, or, in one case, even two days earUer, 

 the young cuckoo has grown so that it completely fills the nest. 



On the loth day the remiges and rectrices are noticeably longer than 

 the rest of the plumage. From this stage on until the chick leaves 

 the nest, the changes are only matters of rapid growth. The feet are 

 now yellow, whereas originally they were flesh colored. 



By the time it leaves the nest the cuckoo has grown in weight more 

 than 11 times its hatching size. Liversidge's bu'd weighed 4.9 grams 

 at bu'th and nearly 60 grams when it left the nest. 



Aside from the purely physical development of the bird, as outlined 

 above, Liversidge has put on record some highly interesting observa- 

 tions of the growth and change of its behavior. For the first five 

 days, as noted in our discussion of the evicting instinct, the chick 

 reacts to nest-mates (eggs or other chicks) by getting them on its 

 back and pushing them out of the nest. This reaction is very weak 

 on the first day, very strong on the second, and normall}^ ceases on 

 the fourth day, but it can still be evoked by artificial stimulation on 

 the fifth day. During this period the gaping response of the chick 

 is usually straight up in direction. 



A second stage begins with the parting of the skin over the eyes. 

 Gaping is now directed toward the entrance of the nest, i. e., toward 

 the direction of the hght, rather than merely upwards, and may be 

 induced by either touching and sUghtly jarring the nest or by a sharp 

 whistled sound near the nest. Liversidge, however, considers that 

 this directional gaping is more the result of an originally conditioned 

 stimulus than of a visually oriented one. The location of the nest 

 necessitated the same approach by the foster parents when visiting 

 it, and gaping became directed toward the entrance. It is true, 

 however, that the gaping did become more directional at the time 

 the eyes began to open, even though the first day or so they were 

 not open enough to give the chick really effective or efficient vision. 

 Both Liversidge and Reed observed the first threatening reactions on 

 the eighth or ninth days. Reed noted that the chick erected the 

 feathers of the head and neck and opened the bill, revealing the 



