MIGRATORY THRUSH. 443 



In the course of my studies, I have, in a great number of instances, ob- 

 served that such birds as produced three broods in one season and in the 

 same district, were all much older than those which produced only one 

 brood. Of this any one can easily assiu-e himself by shooting the 

 breeding birds, and either bending or breaking their bones, or tearing 

 asunder their pectoral muscles, which will be found harder or tougher 

 in proportion to their age. Thus I am inclined to believe, that the far- 

 ther south breeding individuals are found the younger they are, and nice 

 versa. This general rule is well exhibited in most of the species of birds, 

 whether of the land or of the water, that are known to proceed in spring 

 northward, and to return southward at the appearance of the inclement 

 season ; for in them the gradual progress of the young may easily be 

 compared with the much slower advance of the old. 



I have, on many occasions, when certain species returned to the 

 nest or spot where they bred the previous season, observed, that what 

 I considered to be the parents of the first yeai-'s young, were again the 

 occupants. In the Swallow tribe, and in some of our travelling Wood- 

 peckers, as well as in the Summer Duck, the Dusky Duck, the Mallard, 

 the Hooded Merganser, Crow Blackbirds, Starlings, Kingfishers, Ca- 

 nada Geese, &c., this has proved correct, in as far as I could ascertain 

 by the comparative softness of their bones and pectoral muscles. I think, 

 further, that such species as merely enter the southern parts of our 

 country in the breeding season, as the Mississippi Kites, Fork-tailed 

 Hawks, Roseate Spoonbills, Flamingoes, Scarlet Ibises, &c. would 

 all prove, if their winter retreats were well ascertained, to ad- 

 vance much farther southward than any of those which reach us first, 

 and which continue their movements northward ; with the exception 

 of such species, however, as would not be likely to meet with the food 

 they are accustomed to live upon, or the same degree of warmth as that 

 to which they have been habituated, as our Parrakeets, the White- 

 headed Pigeon, Zenaida Dove, Booby Gannet, several Terns, Galli- 

 nules, HeronSj and others, which are by no means deficient in the 

 power of flight, were nothing else required. 



Another thought has frequently recurred to me while making ob- 

 servations on the habits of our birds : the nests of all those which ad- 

 vance least to the northward are less bulky than those of the same species 

 found in higher latitudes. This difiference I have not considered alto- 

 gether as depending upon the state of the temperature, but upon the 



