Reproductive biology

Unlike many Australian passerines, southern logrunners concentrate much of their breeding in the winter. Starting in about April or June their nesting season continues through to August or September, sometimes as late as October. The female is responsible for building the nest and incubating the eggs, and she provides most of the care for the young.

The nest is a globular dome, usually placed on the ground but on occasion may be situated in low vines or on a fallen log or a stump. The female builds a platform up to 2 in (5 cm) of short, thick sticks. She adds curving sides until these meet and join at the top, finally capping this with dry leaves and green moss. This roof hangs over the side entrance, partially concealing it and keeping the interior of the nest dry, even in heavy downpours. The clutch characteristically comprises two eggs, which are large and white. Usually these hatch after a 21-25 day incubation period. The female has most of the responsibility for feeding the nestlings, but she is assisted by the male; he passes food to her, which she in turn gives to the young birds. The young remain in nest for 16-18 days. After fledging they are fed by both parents. Juveniles have a mottled breast, which on the subsequent moult acquires the color appropriate to the bird's sex.

The breeding biology of the chowchilla, which was long unknown, was revealed in 1997 by Cliff Frith and his associates. Most aspects are similar to those of the southern lo-grunner, with some important differences. Nesting can occur in any month of the year, peaking in July through December. The nest is the same shape but considerably larger. Only a single egg is laid. Both incubation and nestling periods are longer: 25 days, with 75% of eggs hatching, and 22-27 days, with 67% of young successfully leaving the nest. More than one male may bring food to the female, but males do not themselves feed the chick.

What is known of the breeding in New Guinea logrun-ners is similar, with records from March and November of nests with single eggs.

0 0

Post a comment