NTRODUCTION. 35 



age of increase or decrease of any species in a given locality 

 must be regarded as merely an approximation; but, as these 

 estimates are given by persons of intelligence and experi- 

 ence, the average of their opinions throughout the State must 

 surely approach the actual facts. The results of this investiga- 

 tion are given in part under the heads of the individual species 

 in the histories that follow in parts I and II, and a summary 

 of the percentages of increase and decrease reported in Massa- 

 chusetts is given on pages 504 and 505. 



Many of the suggestions noted in the blanks filled out by 

 correspondents appeared so full of possibilities that they were 

 made the subject of correspondence. Some observers, not 

 content with filling out the blanks, sent in long letters detail- 

 ing their observations and experiences with birds in which 

 they were particularly interested. Others failed to fill out 

 blanks, but sent letters instead. This correspondence con- 

 tinued for three years and is not completed as the book goes 

 to press. It will be seen that the author is so overwhelmed 

 with material that he can publish but a small part of it in 

 this volume, and can merely summarize a still larger part. 

 Much of this interesting and valuable material may never 

 reach the public ; but it has aided the author greatly in reach- 

 ing the conclusions expressed in this volume. A list of those 

 who have filled out and returned the printed circulars will be 

 found on the last pages of this volume. Statements from other 

 correspondents are credited to them in the text. 



