Chapter 5 Feeding Ecology of the Australian Raven on Rottnest Island

(Acanthizidae), robins (Petroicidae) and small honeyeaters (Meliphagidae)(Catterall et al.
1998).
Nest predation is <strong>the</strong> greatest cause <strong>of</strong> nesting mortality in birds (Skutch 1966; Ricklefs
1969, Ford et al. 2001). Nest predation increases in fragmented habitats (Andren 1992;
Piper and Catterall 2004), as <strong>the</strong> habitat becomes more exposed and as predators move in
from neighboring areas. Bird populations in fragmented habitats that are subjected to
extensive nest predation are unlikely to be self-sustaining (Schmidt and Whelan 1999).
Avian predators have been identified as <strong>the</strong> most important nest predators <strong>of</strong> bush birds
(Fulton and Ford 2001; Piper, Catterall and Olsen 2002; Zanette 2002). The <strong>Australian</strong> <strong>Raven</strong>
has been identified as a predator <strong>of</strong> o<strong>the</strong>r bush bird nests (Major et al. 1994; Major et al.
1999; Fulton 2006), but I am unaware <strong>of</strong> any detailed study conducted into <strong>the</strong> effects <strong>of</strong>
nest predation by this species.
1.1 What are bush birds?
The term bush bird, or woodland bird, arouses an image <strong>of</strong> a small, delicate, <strong>of</strong>ten non-
descript passerine (song bird), but <strong>the</strong> category can be applied to all birds that occur in non-
aquatic habitats such as woodlands, scrublands, grasslands, forests and heath. “Bush bird”
also includes larger passerines such as bowerbirds, magpies and corvids; as well as
terrestrial non-passerines for example quails, parrots, raptors, cuckoos and owls. For <strong>the</strong>
context <strong>of</strong> this study I refer to a bush bird to include those species that prefer, for <strong>the</strong> most
part, terrestrial habitats including vegetation fringing water bodies and coastal dunes and
heath. I do not include shorebirds (waders), ducks, gulls, rails, herons and egrets as bush
birds despite that <strong>the</strong>se groups <strong>of</strong> birds may also use terrestrial habitats for foraging,
nesting or roosting. I have selected six passerine bush birds resident on Rottnest Island as a
focus for this study: White-browed Scrubwren Sericornis frontalis; Western Gerygone
Gerygone fusca, Singing Honeyeater Lichenostomus virescens, White-fronted Chat
Epithianura albifrons; Red-caped Robin Petroica goodenovii , and Golden Whistler
Pachycephala pectoralis. These species have been identified as those <strong>of</strong> conservation
concern (Saunders and de Rebeira 2009) on Rottnest Island.
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