INTRODUCTION. 
XXV 
regular times in making their appearance : Great numbers of 
the former were taken in the county of Northumberland the 
latter end of the years 1789 and 1790, before which they had 
not been obferved fo far fouth as that county, and fince that 
time have never been feen there. 
The ages of birds are various, and do not feem to bear the 
fame proportion to the time of acquiring their growth as has 
been remarked with regard to quadrupeds. Mod birds acquire 
their full dimenfions in a few months, and are capable of propa- 
gation the firft fummer after they are hatched. In proportion 
to the fize of their bodies, birds are much more vivacious, and 
live longer, than either man or quadrupeds : Notwithftanding 
the difficulties which arife in afcertaining the ages of birds, 
there are inftances of great longevity in many of them. Geefe 
and Swans have been known to attain the age of one hundred 
or upwards ; Ravens are very long-lived birds, and are faid 
fometimes to exceed a century ; Eagles are fuppofed to arrive 
at a great age; Pigeons are known to live more than twenty 
years ; and even Linnets and other fmall birds have been kept 
in cages from fifteen to twenty years. 
To the* pra&ical Ornithologift there arifes a confiderable gra- 
tification in being able to difcern the diftinguifhing chara&ers of 
birds as they appear at a diilance, whether at reft, or during 
their flight ; for not only every fpecies has fomething peculiar to 
itfelf, but each genus has its own appropriate marks, upon 
which a judicious obferver may difcrimioate with almoft uner- 
ring certainty. Of thefe, the various modes of flight afford 
the moft certain and obvious means of diftindtion, and ihould be 
noted with the moft careful attention. From the bold and lofty 
flight of the Eagle, to the fhort and fudden fittings of the 
Sparrow or the Wren, there is an ample field for the curipus 
inveftigator of Nature, on which he may dwell with inexpref- 
fible delight, tracing the various movements of the feathered 
nations which every where prefent themfelves to his view. The 
notes, or, as it may with more propriety be called, the language, 
of birds, whereby they are enabled to exprefs, in no inconfider- 
