The breeding season diet of wedge-tailed eagles (Aquila audax) in western New South Wales and the influence of Rabbit Calicivirus Disease

Abstract

A total of 2071 individual prey items were identified from 34 active and 55 inactive wedge-tailed eagle nests following the 1995, 1996 and 1997 breeding seasons. Overall, the eagle's diet was comparable to that reported in other studies within semi-arid regions, with rabbits, reptiles and macropods accounting for 47.8, 22.6 and 13.7% of prey items, respectively. In spring 1996 rabbit calicivirus moved into the study area, resulting in a 44-78% reduction in rabbit abundance (Sharp et al. 2001). An index was developed to enable the time since death for individual prey items to be approximated and a historical perspective of the eagle's diet to be constructed. Rabbits constituted 56-69% of dietary items collected during the pre-rabbit calicivirus disease (RCD) samples, but declined to 31% and 16% in the two post-RCD samples. A reciprocal trend was observed for the proportion of reptiles in the diet, which increased from 8-21% of pre-RCD dietary items to 49-54% after the advent of RCD. Similarly, the proportion of avian prey items was observed to increase in the post-RCD samples. These data suggested that prey switching may have occurred following the RCD epizootic. However, a lack of data on the relative abundances of reptiles and birds prevented an understanding of the eagle's functional responses to be developed and definitive conclusions to be drawn. Nevertheless, the eagles were observed to modify their diet to the change in rabbit densities by consuming larger quantities of native prey species. T h e b r e e d i n g -s e a s o n d i e t o f w e d g e -t a i l e d e a g l e s A . S h a r p e t a l .W R 0 0 0 7 7 A . S h a r p , L . G i b s o n , M . N o r t o n , B . R y a n , A . Ma r k s a n d L . S e m e r a r o

Predictors of clutch predation of a globally significant avifauna in New Zealand's braided river ecosystems

“…Such shifts in predator diet following reductions in preferred prey have been commonly observed in other ecosystems in New Zealand (Norbury, 2001) and worldwide (e.g. Erlinge et al, 1983;Angelstam et al, 1984;O'Donoghue et al, 1998;Sharp et al, 2002), often manifesting in increased predation rates of secondary prey (e.g. Haselmayer & Jamieson, 2001) as found here.…”

“…Erlinge et al, 1983;Angelstam et al, 1984;O'Donoghue et al, 1998;Sharp et al, 2002), often manifesting in increased predation rates of secondary prey (e.g. Haselmayer & Jamieson, 2001) as found here.…”

Predation on native birds in New Zealand beech forests: the role of functional relationships between Stoats Mustela erminea and rodents

“…The rates of predation on birds in the two studies were substantially reduced when rodent densities exceeded 75/ha (Dunn 1977) and 150/ha (Tapper 1979). Similar variations in predation rate on birds by predators that normally feed mainly on small rodents and Rabbits Oryctolagus cuniculus have been documented since then, in response to both natural and human‐induced changes in mammalian prey populations (Hogstad 1995, Murphy et al . 1998, Haselmayer & Jamieson 2001, Blomqvist et al .…”

Clever strategists: Australian Magpies vary mobbing strategies, not intensity, relative to different species of predator

“…The Brown Goshawk ( Accipter fasciatus ) would be next since this species is also an avid bird hunter and birds constitute 37–66% of its total diet (Marchant & Higgins, 1993). The Wedge-tailed Eagle ( Aquila audax ) feeds primarily on mammals, birds representing only 10–28% of its diet (Leopold & Wolfe, 1970; Brooker & Ridpath, 1980; Baker-Gabb, 1984; Sharp et al, 2002) and may, perhaps, be a lesser threat to magpies than any of the other raptors.…”