552 



SCIENCE. 



[N. S. Vol. XIX. No. 483. 



.seemed as solicitous for tlie young song spar- 

 rows as slie had Iieen for tlie young of her own 

 kind, and so far as I could see, she did every- 

 tliing in her power to rear her foster-children. 

 In spite of all her efforts, when the song spar- 

 rows attained an age of about six days, and 

 were just beginning to show feathers, one by 

 one they weakened and died, though both the 

 parent canaries, cock and hen, fed and brooded 

 them constantly. 



Later in the same season I secured a clutch 

 of four field sparrow's eggs (Sipizella pusilla), 

 and gave them to another equally good pair 

 of parent canaries. The results were almost 

 identical with the case cited above; the eggs 

 were all liatched, the young seemed strong 

 and vigorous, the foster-parents appeared to 

 do everything conducive to their develop- 

 ment, but all of the young died during the 

 first week after they were hatched from the 

 egg. This concluded my efforts in this direc- 

 tion for the spring of 1901. In the month 

 of May, 1902, I was able to carry on a much 

 more elaborate series of experiments, which I 

 will now summarize. Some of these, in the 

 light of my former exijerience, I conducted 

 under slightly varying conditions, which I 

 thought might yield more definite results. On 

 May 11, 1902, I found in a field on the ground 

 a nest of field sparrows, the female sitting on 

 four eggs, and there were, at the same time, 

 two larger eggs in the nest, which I took to be 

 those of the eowbird (Molothrus ater). The 

 nest and eggs I brought to the house, keeping 

 them warm, and placed the four field spar- 

 row's eggs under a hen canary which was 

 sitting, and the two cowbird's eggs I gave 

 to another canary. Both females covered the 

 new eggs which had been introduced into 

 their nest, and brooded them within a moment 

 after I had left them. The four field spar- 

 row's eggs, placed under the first canary, be- 

 gan to hatch on the morning of May 22. I 

 had left one canary bird's egg in this nest, 

 and this also was hatched early the next day. 

 Another of the field sparrow's eggs hatched 

 late on May 22, and in the morning of 

 May 23 there were in the nest one canary 

 and three field sparrows, and one unhatched 

 egg of a field sparrow. On May 21 I dis- 



covered the three field sparrows dead in the 

 nest, but the young canary bird was flourish- 

 ing, and in the course of time grew up to 

 maturity under its parents' care. 



To return to the cowbird's eggs in the same 

 clutch ; both of these eggs were hatched on 

 the morning of the twenty-second, and, also, 

 two canary bird's eggs which I had left with 

 them, so that there were two cowbirds and two 

 young canary birds in the nest. Throughout 

 the day and on the succeeding one the parent 

 • birds paid close attention to the brood, and 

 the young birds, I could see, were strong and 

 hearty, as all four of them raised their heads 

 to be fed, and seemed to be treated precisely 

 alike by the two parent canaries. The same 

 conditions prevailed on May 24. On the 

 morning of May 25 the birds were doing well 

 and had grown rapidly. On the afternoon of 

 May 25 one of the cowbirds died, though the 

 other was still strong, and with the two young 

 canary birds was constantly fed by the 

 parents. On May 25 the second eowbird died, 

 and I introduced two young chipping spar- 

 rows, apparently of about the same age as the 

 two young canaries, to take the place of the 

 two cowbirds. I saw the old canary bird at once 

 feed the two sparrows as she did her own birds, 

 and during the day a young man, whom I had 

 posted to watch the proceedings, reported that 

 they were constantly fed. On May 27 the two 

 young sparrows were strong and healthy, as 

 well as the young canaries. The same condi- 

 tions prevailed on the twenty-eighth, and on 

 the twenty-ninth of the month. On May 30 

 one of the sparrows died and was removed, 

 the other appeared strong and healthy, and 

 so far fledged that its species could be dis- 

 criminated. The old birds fed the remain- 

 ing young one throughout the day as well as 

 the young canaries. On May 31 the young 

 sparrow and the canaries were vigorous and 

 flourishing. This condition of affairs was 

 maintained until June 2. On June 2 I found 

 the single sparrow so far grown as to be able 

 to leave the nest, though the two canaries were 

 not so far advanced. At eleven o'clock the 

 young sparrow left the nest and hopped about 

 the floor of the cage ; after an hour I put him 

 back in the nest, where he remained till the 



