THE BIRDS OF AUSTRALIA. 
and which is clotted with scrub, the birds choose sites in accordance with 
the above conditions as far as possible. Many mounds are found in the 
troughs between the sand-dunes in the Mallee or in depressions in these arid 
places, yet there are many exceptions to this rule. The theory that the mounds 
are placed in these depressions so as to get a greater supply of moisture to aid 
in the fermentative action does not hold good. The mounds are placed in 
these sites for protection from the wind as well as to obtain the advantage of 
the higher and more even temperature prevailing in these miniature valleys. 
“ The foundation of the mound of the Leipoa, which is the smallest structure 
of all the Australian mound builders, is formed by first scratching out a circular 
depression in the ground about 2 feet wide and 1 foot deep. The sand or 
gravel is next scraped up and placed around this circular hollow, and so the 
outside waU of the nesting mound is formed. When completed the height 
of the mound ranges from 2 feet 6 inches to 3 feet 6 inches, with a diameter 
at the base of between 12 feet and 18 feet. The size of the mounds vary 
from 110 cubic feet of material to 200 cubic feet. Only a pair of birds work 
at the same mound, and into the concavity, which now has the appearance of 
the crater of a miniature volcano, they scrape leaves, vegetable matter, 
brambles, bits of bark and small branches, and heap it up in a circular fashion 
to a height of from 18 inches to 2 feet. The material is raked and swept up 
by the birds from every convenient direction around about the mound, and 
is often brought a distance of 40 or 50 yards. The manner in which they sweep 
up this debris with their wings and breast, and also rake it, as it were, with 
their powerful legs, and the clear appearance which the ground afterwards 
presents, gives an impression that some gardener had been cleaning up the 
garden with a fine-toothed rake. The wings of the birds are much worn by this 
sweeping. The vegetable material in the centre of the now saucer-shaped 
mound is left for about four or five months uncovered, during which time it 
usually receives a good soaking by the winter rains, which cause decomposition 
to set up and change it into a regular hot-bed. That the Leipoa prepares 
the mound months ahead of the egg-laying period is a remarkable trait in this 
bird’s character, evidencing the knowledge possessed by it of the seasonal 
changes, as well as the physical requirements necessary to set in motion the 
fermentative action. Six to nine days before the hen commences to lay, the 
egg chamber is formed in the centre of all this vegetable matter. A hole, 
ranging from 14 inches to 20 inches in diameter and 18 inches to 2 feet in 
depth, is scratched out by the female. The sides of the hole forming the egg 
chamber being usually hard and well defined, consisting as it does of interlaced 
sticks matted together with leaves and twigs. This condition of the walls of the 
chamber has an important bearing on the future welfare of the eggs. In 
the first place, the foundation and inner walls of the mound being solid and 
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