20 
AMERICAN ROBIN OR MIGRATORY THRUSH. 
birds for rearing their young, the oli} and strong individuals arriving at an 
early period of the season, so that they have abundance of time to rear their 
broods before a decided change of temperature 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 encroached upon the original occupants as 'to force them 'to 
seek other retreats. 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 pro- 
duced by the increase of civilized men. This I would look upon as a proof 
that migration is not caused solely by an organic or instinctive impulse which 
induces birds to remove at a particular period to a distant part, to spend a 
season there for the purpose of reproducing only ; but also for the reasons 
stated above. 
Dr. T. M. Brewer has favoured me with the following remarks : — “ Your 
account of the Robin 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 
Newport, Rhode Island. Such a situation is certainly unusual, if not 
altogether unprecedented. It appears to me that the opinion commonly 
entertained, that the Robin passes the winter in Massachusetts, 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 individuals 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 until 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, 
raspberries, 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 eggs 
last laid to be only about a third of the size of the others. Albinoes of this 
species have sometimes been seen.” . 
The interior of the mouth has the same general structure as that of the 
Mocking-bird ; its width 4 twelfths. The tongue is 8 twelfths long, narrow, 
tapering, thin, horny, with the margins slightly lacerated, and the tip slit. 
The posterior aperture of the nares is oblongo-liuear, 7 twelfths long. The 
