Accordingly, the usual month of nidification throughout the country is 
the month of April. From North Carolina, north through the Atlantic 
states, there is a gradual increase in the dates to New England, and west 
from the Middle states to the boundary of the Humid Province, with the 
exception of Illinois, southern Wisconsin, and Iowa. The latter av¬ 
eraging earlier than Pennsylvania, which may be accounted for by the 
absence of notes on large series from any one locality, the numerous but 
short reports from this section of the country containing records of the 
earliest sets only. In the Arid Province, California averages later than 
North Carolina, with Oregon and Washington but two days later than 
New England. The given average in the Arid Province, with the excep¬ 
tion of California, can hardly be relied upon, by reason of the small 
amount of material collected. 
Incubation. —It has been seen that the nesting period extends from 
early March to late June, and that climatic and seasonal conditions 
greatly influence the birds. Plence, it is evident that to ascertain the 
correct period of incubation would require considerable self-denial or an 
unusual talent for original investigation on the part of the amateur. 
Therefore it is not at all surprising that nothing of value has been re¬ 
ceived bearing on this subject. I have found the period of incubation to 
be about fourteen days ; but the difficulty of making observations, coupled 
with the lack of sufficient time to visit the nest whilst the parent bird 
was off in search of food, and the consequent meagerness of data, com¬ 
pels me to state that I am by no means sure that this is the average period. 
Many ornithologists lack the opportunity and others the inclination to 
penetrate the mysteries of this neglected branch of the science. While 
we might have fewer eggs to hoard in our cabinets, or proudly exhibit to 
our oft-times overcurious friends and neighbors, we might secure notes 
of far greater value from a scientific stand point, and at the same time 
show our love for the science, if we would pay more attention to this point 
That this subject is not open to all is evident. It requires a thorough 
knowledge of the habits of the species under observation, unlimited time, 
much patience and often considerable wood craft, with too often disap¬ 
pointment and defeat the only reward. 
Measurements. — “The majority of widely distributed species are 
more or less affected by geographical variations, from varying influences 
of climate and other surroundings ." — Robert Ridgzvny. If this be true 
in relation to the birds, and the researches by our most eminent scientists 
have proven it to be so, it must almost necessarily hold good in respect to 
their nests and eggs. While the nest must vary indefinitely in accord- 
