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THE POPULAR SCIENCE MONTHLY 



It must be noticed, however, that the goldfinches, referred to above, 

 afford a partial exception to this rule. The young at the two nests of 

 this species, which I have studied, were invariably fed with a white or 

 greenish, sometimes frothy, semi-liquid seed-pap, each bird getting 

 some, and at times from two to four doses, at each visit. Such birds 

 react with great uniformity, and are remarkably uniform in their 

 growth (Figs. 9 and 10). The feeding is extremely rapid, and so 

 little of the pap is ever lost, that on only one or two occasions have I 

 been able to get a drop of it for examination. It consisted of very 

 small, immature seeds of some plant like the bull thistle or mullein. 



Pig. 6. Cedarbied beginning to Regurgitate. Final stage in reaction (opening 



response) of young. Feeding is by regurgitation and direct, several 



being fed at each visit. 



While all the common passerine birds of the country feed their young 

 in the way described, at nests of the cuckoos a most singular and re- 

 markable performance may be witnessed, for these interesting birds 

 not only test the throats of their clamoring brood in the usual way, 

 but practise what may be called mouth-feeding also. Thus we have 

 repeatedly seen the female black-billed cuckoo bring to her nest cater- 

 pillars, or larvas of some of the larger moths, from two or three inches 

 long, already limp, and pinched at a point just behind the head. At 

 the food response or opening reaction, she would lay the insect in the 

 mouth of the young one, and without relaxing her grip, hold it there, 

 mother and child standing immovable from two to five minutes by 



