Reproductive biology

For many New Guinea species, breeding begins late in the dry season, extending into the first half of the wet season. In temperate regions, breeding is from late winter-early spring through mid to late summer. Arid zone species are more opportunistic, breeding as conditions permit. Most have a single brood per season; some attempt two or three clutches.

In the golden whistler and gray shrike-thrush, both male and female contribute to nest construction, incubation of eggs, and care of young. The rufous whistler is similar, except that the female builds the nest. In shrike-tits, the female does most nest construction and incubation, and both adults care for young; additional birds serve as helpers at the nest. Helpers are also known for the whitehead (Mohoua albicilla), in which the female builds the nest. Incubation may be by both parents at some nests or by the female at others. The latter tend to be nests with helpers. After hatching, the chicks are fed by the parents and the helpers.

In the whistlers, the nest can range from the substantial bowl built by the red-lored whistler (Pachycephala rufogularis) to the thin, flimsy cup of the mangrove whistler. Twigs and bark comprise much of the coarsely constructed nest of many species. In habitats with taller trees, nests may be higher, up to 33 ft (10 m) in the case of the rufous whistler. Species from more arid areas, where trees are shorter, and those favoring low, dense shrubs, often place the nest within 3 ft (100 cm) of the ground. Nests may be situated in a tree fork, shrub, or dense vegetation. The nests of shrike-thrushes, pitohuis, and the crested bellbird resemble those of whistlers, although they are generally larger. The sandstone shrike-thrush, which lives on rugged sandstone escarpments with few trees, places its nest of porcupine grass rootlets on a cliff edge or in a crevice. Compared to the nests of most members of this family, those of shrike-tits are made of finer material. The deep cup or goblet is constructed of finely shredded bark bound with spider web and lined with bark and grass. Nests of the New Zealand species of Mohoua are also made of finer material. Moss, lichens, bark strips, and leaf skeletons are used to make a compact cup, bound with spider web. This is usually placed in a fork, but may be suspended from small branches. The crested bellbird has the unusual habit of placing paralyzed caterpillars around the rim of the nest during incubation; the purpose of this behavior is unknown. Clutch size, where known, is two to three, sometimes four, eggs. These are covered with spots and blotches, but the color of these, and that of the background, vary considerably within the family. The background may be white, light to dark pink, cream, buff, olive, or salmon, with markings of black, browns, brick, or lavender. Incubation and fledgling periods are unrecorded for many, perhaps most, species. Where these are known, incubation varies from 14 in some whistlers to 21 days in the brown creeper (Mohoua novaeseelandiae). The nesting period also lasts 14-21 days.

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