NSW Bitou Bush Threat Abatement Plan - Department of ...

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Threat Abatement Plan - Invasion of native plant communities by Chrysanthemoides monilifera
Committee in its determination of bitou bush as a KTP (NSW SC 1999a). The determination
identified three threatened fauna species potentially at risk from bitou bush, namely the eastern
bristlebird (Dasyornis brachypterus), little tern (Sterna albifrons) and beach stone-curlew (Esacus
neglectus).
Anecdotal and observational evidence suggests that bitou bush invasion can result in the decline
of some native bird populations, for example those that nest or roost in hind-dunes such as little
terns (S. albifrons: Ross pers. comm.). In addition, monthly counts of shorebirds on Pelican
Island, off Port Macquarie showed that as bitou bush and lantana increased on the island, bird
densities declined (NPWS 2002a). The contribution of bitou bush and lantana to this decline,
while suspected, is unknown. The effects of bitou bush invasion on bird communities are not
consistent across bird species. On the South Coast, canopy-feeding generalists and understorey
insectivores were found to be more abundant in some bitou bush infested areas than some areas of
native vegetation (French and Zubovic 1997).
The sprawling branches, dense foliage cover, long flowering period and abundant fleshy fruit
production of bitou bush may provide shelter and food for some animals (French and Eardley
1997). However, simply because bitou bush offers a potential food resource does not mean that
animals utilise or prefer this resource to their typical diet. The presence of bitou bush did not
appear to affect fruit removal rates by birds for co-occurring native shrub species (Gosper et al.
2005). Bitou bush may only be a minor food resource for birds, as fruits are only present for a
short period of the year, however during fruiting, this temporary food source may be exploited by
generalist feeders, rather than specialists as highlighted by the list of species reported to consume
bitou bush fruits (Dodkin and Gilmore 1984 and Table 5.1).
Not all bird species that consume bitou bush fruits are effective dispersers (e.g. crimson rosella
(Platycercus elegans)), and for many other birds effective dispersal is only assumed (e.g. from the
occurrence of bitou bush plants beneath emergent trees/perching sites). European red foxes
(Vulpes vulpes) consume high quantities of bitou bush fruits and are effective dispersers of its
seeds (Meek 1998). Unlike many native coastal plants, bitou bush flowers in winter and provides
an important food source for many animals during late winter/early spring (French and Eardley
1997). Conversely, the reduction in native species that flower in summer due to bitou bush
infestation may result in a food shortage for many animals such as specialist frugivores,
nectarivores and insectivores (Dodkin and Gilmore 1984). Twenty-three bird species and three
mammal species have been reported to feed on bitou bush (Table 5.1).
French and Zubovic (1997) recommend further study to elucidate the responses of individual bird
species to bitou bush invasions. Of particular concern is the role of coastal habitats in providing
sources of nectar for fauna over winter, a period of regional shortage, following bitou bush
invasion and competition (Dodkin and Gilmore 1984; Law et al. 2000; Gosper 2004b). Similar
studies for mammals are also needed, especially given that the only mammal species for which
there is information are introduced ones, and nectar/pollen feeding bats (see Table 5.1).
Subsequent to the release of the draft TAP (see DEC 2004), information has been compiled on
fauna species which may be at risk from bitou bush invasion (Table 5.2). Unfortunately, most of
this information was not available prior to completion of this plan and thus no assessments have
been made of the exact nature of the threat or how the impacts due to bitou bush invasion might
be reduced or sites where control will be beneficial. In addition, it appears that the WINS
assessment tool (see Downey in press) may also be useful in determining fauna at risk, based on