EGGS AND EGG-COLLECTING. 1] 
Still further, where birds are conspicuous in colour they 
either build covered nests, or place them in such situations 
as afford safety, and are thus equivalent. For instance, the 
Woodpecker, Kingfisher, and Magpie, the two former having 
a double object in the selection of a situation, firstly their 
own eminently brilliant colours, and secondly their pure white 
eggs. The latter building a covered nest of such materials 
as thorns, seems to point to a strategic planning against 
the immorality of the family to which he belongs. 
Periods of Incubation and their Utility.—The 
Duck family all lay eggs white, or nearly approaching it, 
and take the precaution to cover them carefully on leaving 
the nest. 
Some naturalists have been of opinion that this is to 
prevent an undue escape of the heat generated by the 
parent ; however, I am unable to find any observations to 
prove that these birds leave their eggs for feeding purposes 
longer than any others that hatch their young in three 
weeks. Neither does it appear that they transmit heat better 
or worse than birds of entirely different habits, for it takes 
a Fowl four weeks to hatch a Duck’s egg, and a Duck will 
on the other hand hatch a Fowl’s in the normal time, three 
weeks. It appears that the period of incubation is regulated 
with a great amount of precision by the contemplated 
habits of life, the difficulties to be overcome, and dangers 
to be endured, as the following facts show :— 
A Pigeon hatches its young out in sixteen days, and 
by a special process and careful assiduity feeds them until 
they are almost full grown. A Fowl, though not capable 
of feeding her young in the same way, possesses the power 
of defending her offspring, finding and selecting suitable 
food, and attending to their education generally in a higher 
