42 USEFUL BIRDS. 



fluids ; the chyle is drawn off by the lacteals, and the residue 

 is excreted. The viijor, perfection, and rai)idity of these 

 processes in insect-eatino- l)irds are such as might be expected 

 among animals of such high temperature, perfect respiration, 

 and rapid circulation. 



The various dilations of the digestive tract serve well their 

 [)urpose of enabling the bird to consume the large amount 

 of food necessary for its maintenance. Digestion is partic- 

 ularlv rapid in the growing young of most birds, for thc}^ 

 re{juire not only food sufficient to sustain life, but an extra 

 su})plv as well to enable them to increase daily in size, and 

 to grow, in a few days, those wonderful ai)pendages that we 

 call feathers. 



The Growth of Young Birds. 



The growth of many birds from the e^g to the hour of 

 flight requires less time than is needed by some insects to 

 reach the flight stage. It is most significant that young birds 

 can develop as rapidly as can many in- 

 sects on which they feed, for it shows how 

 readily, under favorable conditions, the 

 increase of birds might keep })r()p()rtion- 

 ate pace with that of insects. AVeed and 

 Dearborn, in their interesting manual, en- 

 ^'.f ■ ^^•~T''""".^!^"'' titled ''Birds in their Relations to Man," 



r.ird on Its first day, 



naked, blind, and help- state that thcv Watchcd four yOUllg SoUg 



less, with niduth open (-, . i / i_ f l_^ ^ j_i 



for food. Kediiced; ^I'^rrows that wcrc out ot tlic ucst ou the 

 after Herrick. eighth day. Mr. Owen records another 



instance Avliere a lirood of }'oung Song Sparrows were 

 fledged and left the nest within the same period.^ Probably 

 this is exceptional ; but many of the smaller birds rear their 

 A'ouno- from the cog to the first flight within two or three 

 Aveeks. ]Mr. Owen found that on one particular day this 

 family of five young Song Sparrows increased in average 

 weiii'ht fortv-eiffht i)er cent., while the smallest bird gained 

 fifty-five per cent, in a single day. 



The young of perching birds (Insessores) come into the 

 Avorld tiny creatures, either naked or covered with down, 



' A Family of Nestlings, by D. E. Owen. The Auk, Vol. XVI, No. 3, July, 

 1899, pp. 221-225. 



