PARENTAL INSTINCT IN BIRDS. 249 
affords an illustration of the idea that birds with no parental 
instinct lay large quantities of eggs. 
An extreme case of “‘ physiological affection”’ is met with in 
the Emperor Penguin of the Antarctic Regions. The females 
are so filled with a desire to sit that, according to Capt. Scott, 
they line up behind a sitting female so as to be ready to take 
her place whenever she rises to leave the egg. . 
IT wonder that more species have not adopted the happy-go- 
lucky and lazy method of the Owls in not waiting till the full 
clutch is laid before they sit. The females sit as soon as an egg 
makes an appearance. The benefits of this are clear as day- 
light. It lessens the labour of the parents in hunting for and 
providing food for five helpless young at once, while the incuba- 
tion is cut short as the warmth from the bodies of the nestlings 
keeps up the incubation temperature of the unhatched eggs. 
Probably this is adopted more often than is usually thought. 
The eggs get buried beneath the young, and the observer, as a 
rule, is satisfied without lifting them to look beneath. I found 
‘Tree-Pipits’, a Red-backed Shrike’s, and Chaffinches’ nests this 
year with eggs buried beneath well-developed young. The eggs 
hatched subsequently. 
Il.—OrHer Aspects. 
Concurrently with the development of the incubation instinct 
arose the nest-building habit, the chief factors directing which 
probably were the personal comfort of the sitting bird first, then 
the protection of the young, and finally the esthetic taste of the 
builders. If a female can choose and detect minute differences 
in form and colour of the males, surely she exercises those 
powers in the construction of her nest ! 
All birds were formerly ground-birds most probably. Most 
of the ground-builders of to-day do little else than breast a 
hollow in the sand or scrape one in the earth. Subsequently 
they were driven to the trees, or to holes in the earth and in 
timber. 
When once the parental instinct had secured a firm founda- 
tion, and the ties between birds and their offspring became 
strong and close, all those remarkable tactics, such as the 
lame devices of the Ducks and Plovers, would be evolved. I 
