Bregulla Cont......
tends to run quickly into the undergrowth at the slightest disturbance. It
will fly if surprised but often just to the lower branches of a nearby
tree. It is able to fly well, with deliberate wingbeats and intermittent
glides, and may visit offshore islands to roost. Some concentrations of
these birds may occur around the larger laying sites but they disperse
after the laying period. They roost at night in high thick scrub or trees,
pairs usually on the same branch together.
VOICE
It is quite vocal at times, usually a subdued or loud hoarse clucking. A
loud call can be heard particularly at dawn and dusk and even at intervals
through the night. Pairs may call in duet or several birds in concert for
long periods possibly advertising their territories. A loud, two-syllabled,
somewhat slurred and far-carrying call 'took-tooorrr' may be repeated for
long periods; first syllable short, second drawn-out and decreasing in
volume near the end. Feeding pairs emit soft, short notes at irregular
intervals.
FOOD
Insects, grubs, worms, snails and other invertebrates are taken. They also
eat fruit, seeds and other vegetable matter.
NEST AND BREEDING
In Vanuatu two methods of incubation are apparently used. On islands with
active volcanoes, according to the village people, the hens bury their eggs
in a number of communal sites scattered in the vicinity of the craters;
volcanic heat vents and the availability of loose soil determine these
areas. Most of their egg-laying sites are however, scattered throughout the
lowland forest often near the coast. Sites vary 'considerably in size,
commonly a few metres in diameter but they may be up to 10 m wide. The
smallest measured was less than half a metre and visited by only one hen.
The Incubator Bird may use the same site year after year and some mounds,
which Are frequented by a number of hens and are excavated repeatedly, have
served countless generations and become larger and deeper with time.
The majority of birds bury their eggs around the base of large decaying,
forest trees where the heat generated by the fermenting vegetable matter
mixed with earth and/or sand, incubates the eggs. It is not clear which
factors determine the locality of the laying site, perhaps the soil is not
so compacted between the roots and more suitable for burrowing or perhaps
they do not have to dig so deep to reach an adequate temperature for
incubation. Eggs are laid at different depths and it has not been
established yet if the female Incubator Bird can detect the temperature of
the soil. A laying site typically consists of a series of discrete
excavations scattered over the area. The period of greatest activity is the
morning with birds arriving early to dig their burrows but some may also
visit the site later in the day. They usually walk round for a while and
scratch in a few places first before beginning to dig in earnest. Pairs may
visit the site together but the female digs the burrow, using both feet
alternately, scratching into the material of the mound and pushing it
backwards with shovel-like claws. As the burrow deepens the hen reappears
at the entrance at intervals and looks around and when the excavation is
complete remains inside for about 30 or more minutes while she lays a
single egg which may be positioned vertically or almost
horizontally. The burrow is then filled with small roots, rotting leaves,
other forest litter and soil scratched from the burrow and the surrounding
forest floor. These burrows may be 0-3 to 1.2 m deep, Up to 2 M long and
have an entrance of about 0-4m in diameter. The bird returns a few days
later to deposit another egg which is laid in a separate burrow. In the
cases observed the time taken for the whole process involved varied
considerably and took between 2 and 4 hours.
The long oval eggs are pale to pinkish-brown when newly laid but may soon
become stained with rotting vegetation. They are very large in relation to
the adult bird and contain a high proportion of yolk. Twenty eggs examined
were found to be 77 to 85 mm long with a diameter Of 43 to 47 mm and
weighed from 50 to 70 g. The exact length of incubation is not known,
probably varying with slight differences in temperature, but it is over 45
days. It was not possible to measure temperatures in the mounds. Studies of
the Niuafo'ou Megapode Megapodius ptitchardii which is endemic to Niuafo'ou
(Tonga) give incubation periods from 47 to 5 i days and records show that
the soil temperature in the immediate vicinity of the eggs varied between
29'C and 38'C (T'odd, 1982-83). Data for other Megapodius- spp are
generally in the same range (Crome and Brown, 1979 and Campbell and Lack
1985)-
The chicks are independent on hatching and use their powerful feet and long
claws to dig their way upwards to the air through the mound. Even so the
process may take hours and once on the surface they often rest for a while
before taking to the shelter of the undergrowth. From the moment they
emerge the precocious chicks are able to fend for themselves and to fly if
the need arises but they usually remain hidden, resting for the first day
or so before becoming active and feeding. There are often a few chicks that
die naturally at different stages of development in the egg-shell. The
thickness of the layer and density of the nest material probably has a
bearing on this and the frequent digging and shifting of material in the
mound as new burrows are made may be in part responsible.
In Vanuatu, according to the village people, freshly laid eggs of the
Incubator Bird can be found in every month of the year suggesting that the
breeding cycles of the individual females are asynchronous and similar in
this respect to the Orange-footed Scrubfowl Megapodius freycinet
(reinwardt). The number of eggs laid by one female and the intervals
between successive eggs is not known in Vanuatu but an Orange-footed
Scrubfowl in northern Queensland has been recorded as laying 1 2 or
possibly I 3 eggs at intervals ranging from 9 to 2o days (Crome and Brown,
1979)-
The End.
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