Nesting biology of the spotted catbird, Ailuroedus melanotis, a monogamous bowerbird (Ptilonorhynchidae), in Australian Wet Tropics upland rainforests
Authors: Frith Clifford B. , Frith Dawn W. 
Published: September 2002

Spotted catbird, Ailuroedus melanotis, nests (104 active
and 59 old) were studied on the Paluma Range, north Queensland during
1978–89. Nesting began in September: 97% of clutches were
incubated during October–December, 83% of nests had nestlings
during November–December, and 70% of nestlings fledged in
December. Nests were 3.1 1.3 m (n = 119) above
ground. Nest dispersion was clumped, reflecting preference for particular
topography and traditional use of a site over years. Four individuals used the
same nest location for at least four consecutive seasons. Mean
nearest-neighbour distance between 30 nests, built at 11 traditional locations
over different seasons, averaged 42.0 31.4 m. At least 32 pairs nested within
50 ha in season 1980–81, at an average of one pair per 1.6 ha (home
range) and at a mean nearest-neighbour nest distance of 96.9 24.8 m. Parents
foraged at a mean of 68 36 m from their nests. Two replacement nests were
built and laid in within 16 days of the loss of a brood. Eggs were laid
9–29 days after nest completion. Mean clutch size was 2.0 and eggs were
laid on alternate days. At laying, eggs averaged 11% of mean adult
female weight. Only females built nests, incubated, and brooded. Males fed
females and nestlings. Females sometimes incubated before clutch completion.
Median and mean incubation periods were 22–23 days. Eggs were incubated
for 62% of total diurnal time, bouts averaging 19 min at a frequency of
2.0 per hour. Median nestling period was 19–20 days, the mean 20 days,
when parents spent an average of 48% of diurnal time at their nest.
Visits to nestlings averaged 4.9 min at a frequency of 5.9 per hour. During
the first 15 days of nestling life, females spent 12% more time
brooding a single nestling than a larger brood. A single nestling was provided
with an average of 3.9 meals per hour and a larger brood 5.7 meals per hour.
On average, females delivered 63% of all meals (n
= 602) to broods at a rate of 3.3 per hour, males doing so at an
average of 2.0 meals per hour. Of 323 identified nestling meals, 80%
were of fruit (at least 33 plant species, of which 29 were identifiable) and
20% animal (of 182 meals 54% were insects, 21% pieces of
birds). Proportionately more fruit was fed to older nestlings. Of 137 eggs
laid in 72 nests, 88% hatched and 60% of nestlings left the
nest; 46% of all eggs produced fledglings, averaging 1.0 per nest.
Overall nest success rate was 51%, but of only those nests for which
the fate was known it was 57%. The success rate of nests for which the
fate was known during an exceptionally dry breeding season was 8%, with
only 5% of eggs laid producing fledglings, at a rate of 0.1 per nest
The nesting biology of the spotted catbird is compared with that of the green
catbird, A. crassirostris, and found to be similar
except in mean nest height and in proportions of fruit/animal foods fed to
nestlings. The nesting biology of these two monogamous species is compared
with that of the polygynous bowerbirds, and the significance of
Ficus figs to the evolution of catbird monogamy
discussed. The limited extent of nest attendance by the male catbird is
discussed in the context of the evolution of contrasting bowerbird mating
systems.