18 INTRODUCTION. 
If inexperienced, do not make exchanges with another inex- 
perienced person, who may unintentionally cheat you, or with 
one unknown to you, who may purposely cheat you. Remember 
that egos often vary greatly in value in different parts of the 
country, and do not accept any price-list as a basis for ex- 
change. Endeavor by energy to arrive at approximate comple- 
tion, have some definite object in view, such as a cabinet 
comprising all the eggs of Massachusetts, and do not unwisely 
form a miscellaneous collection everywhere incomplete. 
§ S. To know the notes of all our birds is a great assistance 
in finding their nests, and in finding, distinguishing, or study- 
ing the birds themselves, who sing chiefly on or soon after 
their arrival from the South, during their migrations, and the 
mating-season in spring, or early summer. It is best to study 
their music at sunrise, or in the early morning (particularly in 
the case of species migrating), and also at evening. Even 
families may (to a limited extent) be classified by their notes. 
To study birds, in relation to their habits or notes, walk in their 
haunts, continually pausing to catch the slightest sound, which, 
if not recognized, should be traced to its source, or to allow 
the birds to gather about or approach you. If necessary, 
follow them silently and persistently, but remember that 
stealthiness sometimes alarms them more than an open 
approach. If several species be together, do not be misled by 
the confusion of their songs, and do not hastily attribute the 
note of one kind to another bird immediately near. Both 
squirrels and ‘‘chipmonks” frequently produce notes, which 
might excusably distract the attention of an unpractised orni- 
thologist. By looking up, especially on very clear days, you 
may often see hawks, or other birds, flying over silently. 
