THE BIRDS OF AUSTRALIA. 
which, owing to the extreme dryness of the air, has become so dry that it 
probably would not set up sufficient heat to incubate its eggs with any degree 
of certainty. During the greater part of the time of incubation the heat of the 
egg chamber is many degrees hotter than the surrounding atmosphere, and 
ranges from 90 to 97 degrees Fahrenheit, whilst the external covering of 
sand on the mound often becomes so hot from the heat of the sun’s rays that 
it is extremely painful for a person to recline on it. When starting to open 
up the mound to deposit its eggs, the bird scratches out a channel all around 
the exterior of the summit of the mound about a foot from the top. Over 
the outer edge of this the birds scrape the material resting on top of the egg 
chamber, and when this has been removed the mound presents the appearance 
of a miniature volcano or funnel. Usually in dull or wet weather the birds 
cap the peak of the mound with sticks placed crosswise in a careless litter, 
evidently to turn aside the water which would percolate to the egg chamber 
and interfere with the proper rate and progress of the fermentation, whilst the 
sticks would help materially to detract from the prominence of the sharp cone 
and so make detection more difficult, as well as preventing the loose sand from 
being scattered by the wind. Thus sticks on the mound are nearly always 
a sign that the birds have started to lay. In warm and sunny days the apex of 
the mound is removed and a concave opening made, so that the warmth of the 
sun’s rays may penetrate and assist in the incubation. 
“ The Leipoa does not start to breed until two years old, and the first clutch 
of eggs laid is notably smaller in size than those laid by aged birds. It is im- 
possible to say with any degree of certainty what is the precise interval between 
the laying of each egg, since in some mounds observations made show that an 
egg was laid every fourth day, in others every fifth day, whilst the record for 
others range from two eggs in eighteen days to three eggs in two and twenty 
days. Usually the Leipoa lays its eggs regularly every third or fourth day during 
the first half of the breeding season, but then the periods between the deposit- 
ing of each subsequent egg varies according to the constitution of the bird 
and the food supply in the vicinity of a particular mound, as well as to other 
conditions. For instance, hot and dry seasons have a noticeable effect on the 
birds, and at these times they lay few eggs. Some of the mounds were 
examined when it had been exceptionally hot and dry, contained from two to 
five eggs, but a great many mounds were found to be deserted. During the laying 
season of 1907 at Pine Plains, Victoria, forty-five different mounds were placed 
under observation at which the birds had been working in the usual manner 
during May and June gathering up the dead leaves, etc., and placing them in the 
egg chamber which the birds had already opened out in the old mounds a week 
or so beforehand. Fifteen of the MaUee hens completed their mounds and started 
to lay early in September, which is the usual month for the birds to start 
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