Egg-Collecting and Its Object 
the habits of a given species should specify whether or not they 
were taken from an individual bird or from numerous individuals 
of that species. 
Among the numerous points to be noticed may be mentioned 
the following : When birds are seen pairing ; when nests are 
commenced ; how long building ; whether built by one or both 
birds ; materials used in the construction, from where gathered ; 
where the nest is placed ; if on the ground, whether on a sod or 
tussock, in a tuft of grass or ina depression, in damp or dry places, 
in open country, in woods or in thickets ; if in a bush, what kind 
of bush ; the height from the ground ; whether in a crotch, sad- 
dled on a branch or pendent ; the size of nests ; when the eggs 
are laid ; interval between laying ; period of incubation ; whether 
both birds or only the female takes part in that duty ; appearance 
of young when hatched, and at different ages ; at what age they 
leave the nest ; which of the parent birds provides the food, or 
whether both do ; of what does the food consist ; what becomes 
of the young when they leave the nest ; and so on with the num- 
berless points which go to differentiate one bird from another. 
The period of incubation varies of course with different birds ; 
for instance, with the white-eyed vireo it is about seven days ; the 
indigo-bird takes ten days, the wood thrush twelve, and the ruffed 
grouse eighteen. The time should be taken from the day the bird 
actually commences sitting and not necessarily from the day on 
which the last egg is laid. Eggs are usually laid during the morn- 
ing, between the hours of nine and eleven, but the bird does not 
always begin to sit the same day that the last egg is laid. Some 
birds commence sitting before laying the full complement of eggs ; 
in these cases the young are hatched at intervals. 
The age at which young birds leave their nests is not de- 
pendent on the s7ze of the bird. The gallinaceous species, such 
as the grouse, quail, turkey, etc., being well developed when 
hatched, desert the nest within a few hours after leaving the egg ; 
the young wood thrushes keep to the nest for ten days, by which 
time they are pretty well feathered, the tail being rather more than 
one inch in length ; the white-eyed vireo leaves when seven days 
old ; while the owls stay in their nest for several weeks. 
A few birds build their nests indiscriminately on the ground 
orin bushes. In some localities certain birds almost invariably 
choose the ground, while in some other place, where conditions 
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