472 MEMOIR OF DANIEL TREAD WELL. 



Can it be that all this food is required to maintain the temperature of the bird some six or 

 eiirht decrees above the standard of the mammalia ? Or are the powers of life, the muscular and 



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nervous energies, and the processes of assimilation and absorption, so much more exalted in birds 

 than in men and beasts? These are questions naturally suggested by the subject, but not to be 

 answered, by me at least. Another question that yet more immediately presents itself is this : 

 How can this immense amount of food required by the young birds be supplied by the parents ? 



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Suppose a pair of old robins with the usual number of four young to a brood. Their youn 

 would require, according to this instance, 250 earth-worms, or their equivalent in insects or 

 other food, a day. Suppose the parents to work 10 hours, or 600 minutes, to procure this food. 

 This would be a worm in every 2 T % minutes, or each parent must procure a worm or its equiv- 

 alent in less than 5 minutes during 10 hours, and this in addition to the food required for its 

 own support. I know that the industry of birds in procuring food for their young has often 

 been noticed ; but I know of nothing equal to the above requirement. I have had three pairs of 

 robins that have raised each pair its brood upon trees within twenty yards of my house during 

 the present season, and I have observed them often ; but I never saw them return to their nests 

 with supplies oftener than once in ten minutes, although they worked with great industry. Not- 

 withstanding all this, the young, four in each brood, were raised successfully, however irrecon- 

 cilable it might seem with what I might have predicted from the quantity of food required by the 



bird raised by me. 



It might be seen that my table of experiments ends with the thirty-second day. The bird 

 had then attained his full size, and was intrusted to the care of a faithful person during my 

 absence on a journey. On my return, after eighteen days, I found it strong and healthy, with no 

 increase of weight, though its feathers had grown longer and smoother. Its food had been 

 weighed daily and averaged 15 pennyweights of meat, beef, veal, or lamb, 2 or 3 earth-worms, 

 and a small quantity of bread each day, the whole equal to 18 pennyweights of beef, or 36 

 pennyweights of earth-worms, and it has continued to eat this amount daily to the present time. 

 I at first attributed the great consumption of food by this bird to the unnatural condition in 

 which it was placed, being in a constant state of excitement very different from the quiet of its 

 nest ; but as it has continued in its confinement, certainly with much less exercise than is taken 

 in the wild state, to eat one third of its weight of clean flesh daily, I concluded that the food that 

 it consumed when young was not much more than must always be provided by the parents of 



wild birds. 



If you find in the preceding narrative no addition to your previous knowledge, and nothing to 

 interest you as a technical naturalist, I think that you will agree with me that every arborist and 

 every admirer of trees may derive from it a lesson showing the immense power of birds to 

 destroy the insects by which our trees — especially our apple trees, elms, and lindens — are every 

 few years stripped of their foliage, and often many of them entirely killed. The food of the robin 

 while with us consists principally of earth-worms, various insects, their larvae and eggs, and 

 a few cherries. Of earth-worms and cherries they can get but few, and those during but a short 

 period, and they are obliged therefore to subsist principally upon canker-worms, some kinds of 

 caterpillars, and bugs, the great destroyers of foliage. Now if each robin, old and young, requires 

 for his daily subsistence and growth an amount of these equal to the weight of earth-worms 

 required by my young bird, what prodigious havoc must be made by a few hundreds of them even 

 upon the insects of the largest orchard or the elms of a whole park. Is it not then a most advan- 

 tageous bargain to us to purchase this service of the robins at the price of a few cherries ? There 

 has been a great improvement in this matter of preserving birds since my remembrance, and, 



