28 ON THE NOTES OF BIRDS. 
Knowledge is acquired slowly; and even the most 
careful and indefatigable inquirers are liable to errors 
and omissions. Much yet remains to be supplied, 
much to be corrected, before the history of British 
birds can be pronounced complete. 
To the practical ornithologist who is desirous of 
promoting and extending his favourite study by the 
communication of his personal observations and re- 
marks, an intimate acquaintance with the various 
notes of the feathered tribes is of such importance, 
that any difficulties he may encounter in obtaining it 
will be more than compensated by the numerous ad- 
vantages it affords. In many instances it enables him 
to detect species which might otherwise elude his ob- 
servation. Thus the Land-Rail (concealed in the long 
grass of luxuriant meadows, where it runs with great 
rapidity, and is sprung with difficulty), the Grass- 
hopper-Warbler (closely embowered in thick hedges 
and bushy dingles, where it employs every artifice to 
escape notice), and the Sedge- Warbler (secluded amid 
the reeds and other aquatic productions of pools and 
marshes) are much more frequently heard than seen, 
the harsh call of the first, the sibilous note of the 
second, and the hurried song of the last; being re- 
peated through the night, in fine weather, during the 
breeding-season. 
It also enables him to identify species with the 
utmost precision ; in some cases, indeed, with greater 
certaimty than he could by the examination of speci- 
