Effect of a major flood on breeding and habitat of the Crimson Finch (Neochmia phaeton)

Abstract

Riparian specialists, such as the Crimson Finch (Estrildidae: Neochmia phaeton), are vulnerable to declines in habitat quality, including alterations of flow regime associated with dam construction. Crimson Finches persisted and bred in substantial numbers following two large floods in the Isaac–Connors catchment in early 2008. Major flooding was not detrimental to nesting and breeding success, although the immediate post-flood period was identified as a bottleneck in the availability of riparian grass seed. Crimson Finches nested at 16m or more above the normal river level (compared with an average of 2–3m elsewhere in Northern Australia); indicating that they have adapted to the extreme flood peaks in the Fitzroy River basin. The tall river-associated grass Chionachne cyathopoda was a key habitat plant, retaining seed well into the dry season when most other grasses are expended. It also provided abundant seeds following floods, coinciding with peaks in abundance of dependent young finches. The adaptations of both Crimson Finches and Chionachne suggest that increased flooding, predicted by climate change, is unlikely to be a problem. In contrast, a proposed dam on the Connors River may be a threat. River regulation that reduces peaks of major floods may favour introduced riparian grasses over flood adapted native grasses such as Chionachne. Any change in the quantity of this species could be detrimental to persistence of Crimson Finches. Environmental managers should carefully consider the ecology of Chionachne when making decisions about river flows