326 
BIKD-LIFE, 
by the passing song, until the well-earned reward is 
won. Each egg demands the same supply of vivifying 
warmth; and to this end the bird rearranges them 
in the nest, so that they either lie with their points 
together or, at any rate, in a circle. The eggs are 
also turned with the beak once a day at least, for every 
part needs warmth. Besides this, the bird is always 
careful to shield them from the heat of the sun when 
this is too fervid. In the nest of the Spur-winged 
Plover (. Hoplopterus ) I always found the eggs surrounded 
with moist earth during the glowing hours of the Egyptian 
noon : this was, without doubt, placed there by the mother 
to shield them from the noxious influence of excessive 
heat. At other times the bird is also well aware how to 
make use of the same. The Ostrich, it is supposed, scarcely 
ever sits on its eggs during the day, but performs that duty 
only at night. The same may be observed of Terns ; and, 
probably, all birds which lay their eggs in the sand act 
in a similar manner. They are, doubtless, aware that 
the latter absorbs an amount of heat at mid-day which is 
almost equivalent to the temperature of their bodies. In 
this respect the method by which the young of the Mound¬ 
raising Megapode (Megapodius) are hatched is most singular. 
They erect curious edifices for this purpose—regular 
artificial incubators! The Englishman, Gilbert, soon 
after his arrival in New Holland, remarked certain sand¬ 
hills some five feet in height and seven in diameter : 
these tumuli the colonists took to be the graves of a 
race of people long since extinct, but were declared by 
the Aborigines to be the breeding establishments of a 
species of bird. After careful investigation the native 
account proved to be the correct one; for Gilbert saw 
eggs taken out of them in his presence, from galleries of 
