INTRODUCTION. xX1X 
In the course of the descriptions of each species, the terms 
Summer and Winter Visitant, and Polar and Equatorial 
Migrant, will frequently occur, which, to general readers, 
“may seem to require explanation. ‘This I will, as briefly as 
possible, attempt. The Summer Visitant, or Polar Migrant, im- 
plies a bird resident, during the summer season, in these king- 
doms, as being included in the northernmost parallel of Lati- 
tude to which its migration extends, from the Equator to- 
wards the Pole*. To the Winter Visitant, or Equatorial 
Migrant, these kingdoms are in the southernmost parallel to 
which their winter’s migration reaches, in course from the 
Pole to the Equator, their summer being passed in higher 
and colder regions +. The term Occasional Visitant, when 
used, denotes a bird found here only at uncertain, and often 
distant intervals}, and will frequently apply to stragglers, 
that have been driven by tempest, or other casualties, out of 
their regular course of migration, either from more southern 
countries than our own to northern regions, or the reverse. 
Migration is an instinctive rule of action stamped upon the 
animal world (but more particularly displayed in the feather- 
ed race, from their superior ability of locomotion), by the 
general and provident Laws of Nature, and which has long 
engaged the attention of the speculative naturalist; but, 
without perhaps the possibility of coming to any conclusion 
* Such are many of the Genus Sylvia, the Cuckoo, Night-Jar, Swallows, 
&c. 
+ Such are most of the Genus Anas, Tringa, Scolopar, and some of the 
Thrushes, with the Snow-Bunting. 
+ The Wax-Wing and Cross-Bill are instances under this head.. 
