Nestling and post-fledging growth and development in an Australian passerine: Hall’s Babbler Pomatostomus halli

Postnatal growth and development has rarely been studied in passerines of the southern hemisphere, particularly Australian species. Developmental changes in external morphology and the growth in body mass and size of nestling and juvenile Hall's Babblers (Pomatostomus halli) were quantified and described. Additionally, a guide to ageing nestlings to the nearest day was developed to facilitate studies of breeding biology. Nestling growth and development in Hall's Babblers were similar to that of its closest relative, the Grey-crowned Babbler P. temporalis. Body mass, skeletal and feather growth, but not the sequence and timing of developmental changes in external morphology, were affected by nestling body condition. Juvenile Hall's Babblers attained adult size by four months of age, and were indistinguishable from adults by one year of age. Nestling growth rate in body mass of Hall's and Grey-crowned Babblers is lower than similarly sized northern hemisphere passerines, but the relative size at fledging is similar. This suggests nestling growth rate may, like other life-history traits, differ between passerines of the southern hemisphere and those of temperate regions of the northern hemisphere. However, since nestling growth has been poorly studied in southern hemisphere passerines, the available data are inadequate to test this hypothesis.

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