INTRODUCTION XI 



has been laid, and then begins to spend nearly all the time 

 on the nest. In such a case the incubation should not be 

 considered as beginning until the last egg was laid and the 

 ■ bird was almost constantly on the nest. On the other hand 

 if the bird remains on the nest nearly all the time after the 

 first egg is laid, then incubation begins with the first egg laid 

 and not with the sixth. If the bird sits only fairly constantly 

 many would say that incubation commenced upon the laying 

 of the first egg, while others would be equally as positive in 

 saying that the bird did not begin incubating until the last 

 egg was laid. In my statements in the text regarding the 

 incubation period I have taken the time from the day when 

 I had reason to believe the female had actually commenced to 

 incubate (regardless of the fact whether the set of eggs was 

 complete or not) to the time when the first egg was hatched. 

 It is quite true that in some cases a nest may have been visited 

 only once on a given day, and a bird supposed to be actually 

 incubating may have happened to be on the nest only for a few 

 minutes at the time when it was visited. It is therefore to be 

 understood that my observations regarding the incubation 

 period are to be taken, subject to such variation as may be 

 produced by errors of judgment due to not correctly under- 

 standing the true conditions in a given case. 



At the end of the work there is given a hypothetical list, 

 including such species as have been recorded from the State 

 and afterward found not clearly entitled to be called birds of 

 Maine, and also including species which may be expected to be 

 taken within our boundaries some time in the future. 



A summary of conclusions, a chapter on faunal areas, and a 

 partial bibliography are also given at the end of the work. 



ORA WILLIS KNIGHT. 

 Bangor, Maine, September 22, 1908. 



