24 
INTRODUCTION* 
(as Mr, Bullock* witnessed in a voyage near to Vera Cruz late in 
autumn,) the famished travellers familiarly crowd the decks of the 
vessel, in the hope of obtaining rest and a scanty meal, preparatory 
to the conclusion of their unpropitious flight. 
Superficial observers, substituting their own ideas for facts, are 
ready to conclude, and frequently assert, that the old and young, 
before leaving, assemble together for mutual departure ; this may be 
true, in many instances, but in as many more a different arrange- 
ment obtains. The young, often instinctively vagrant, herd together 
in separate flocks previous to their departure, and guided alone by 
the innate monition of nature, seek neither the aid nor the company 
of the old ; consequently in some countries flocks of young of par- 
ticular species are alone observed, and in others, far distant, we 
recognise the old. From parental aid, the juvenile company have 
obtained all that nature intended to bestow, existence and education ; 
and they are now thrown upon the world among their numerous com- 
panions, with no other necessary guide than self-preserving instinct. 
In Europe it appears that these bands of the young always affect 
even a warmer climate than the old ; the aeration of their blood 
not being yet complete, they are more sensible to the rigors of cold. 
The season of the year has also its effect on the movements of 
birds ; thus certain species proceed to their northern destination 
more to the eastward in the spring ; and return from it to the south- 
westward in autumn. 
The habitudes and extent of the migrations of birds admit of con- 
siderable variety. Some only fly before the inundating storms of 
winter, and return with the first dawn of spring ; these do not leave 
the continent, and only migrate in quest of food, when it actually 
begins to fail. Among these may be named our common Song 
Sparrow, Chipping Sparrow, Blue-bird, Bobin, Pewee, Cedar-bird, 
Blackbird, Meadow Lark, and many more. Others pass into warmer 
climates in the autumn, after rearing their young. Some are so 
given to wandering, that their choice of a country is only regulated 
by the resources which it offers for subsistence ; such are the Pigeons, 
Herons of several kinds, Snipes, Wild G-eese and Ducks, the wan- 
dering Albatros, and Waxen Chatterer. 
The greater number of birds travel in the night ; some species, 
however, proceed only by day, as the diurnal birds of prey, Crows, 
Pies, Wrens, Creepers, Cross-bills, Larks, Blue-birds, Swallows, and 
* Travels in Mexico. 
