444 MIGRATORY THRUSH. 



longer time afforded these birds for rearing their young, the old and strong 

 individuals arriving at an early period of the season, so that they have abun- 

 dance of time to rear their broods before a decided change of tempera- 

 ture takes place. Again, it has become a matter of great doubt with 

 me, whether the necessity of migration has not, in some parts of our 

 countries, been increased in many species by the great increase of the 

 individuals of a species that have settled there, and which have so en- 

 croached upon the original occupants as to force them to seek other re- 

 treats. In times long gone by, the country was in a manner their own, 

 and being free of annoyance, they probably bred in every portion of the 

 land that proved favourable in regard to food. On the other hand, I 

 am fully aware that many species, now unknown in certain districts, 

 have formerly been abundant there, but have been induced to remove 

 to other sections of the country, enticed thither by the accumulation 

 of food produced by the increase of civilized men. This I would look 

 upon as a proof that migration is not caused by an organic or instinc- 

 tive impulse which induces birds to remove at a particular period to a 

 distant part, to spend a season there for the sole purpose of reproducing, 

 but for the reasons stated above. 



Dr T. M. Brewer has favoured me with the following remarks : — 

 " Your account of the Jiobin hardly leaves me any thing to add, except 

 the fact that Mr Cabot found the nest of this bird on the ground (a bare 

 rock) near New Port, Rhode Island. Such a situation is certainly un- 

 usual, if not altogether unprecedented. It appears to me that the opi- 

 nion commonly entertained, that the Robin passes the winter in Massa- 

 chusetts, is not strictly correct. Sure it is that Robins are to be found 

 here pretty much at all seasons, but I have no idea that the same indi- 

 viduals remain any length of time. They are rather successions of 

 flocks slowly moving towards warmer regions, and have about all passed 

 through the State by the first week of February ; from which time un- 

 til March none are to be found there, when those that visit the extreme 

 northern parts again commence their migrations. In the gardens in 

 the vicinity of Boston, the Robins have become a great nuisance, from 

 the boldness with which they appropriate to their own use the largest, 

 earliest, and best cherries, strawberries, currants, buffalo-berries, rasp- 

 berries, and other fruit. The Robin generally has three broods in a 

 season, in this State, and in the third nest it is not unusual to find the 





