38 South Australian Ornithologist 41 (1)

Ph.D. Thesis Abstracts

Melithreptus species in the Mt Lofty Ranges Comparative Ecology, are sympatric with strikingly similar ecology. and Conservation, of the Melithreptus gularis is the largest of the three, while M. brevirostris and M. lunatus are almost identical Melithreptus Genus in the in weight, feeding behaviour and morphology. Southern Mount Lofty Despite their similarities no studies have closely examined their ecology in sympatry and no studies Ranges, South Australia have examined possible causes of their decline.

Nigel Willoughby Interspecific competition is thought to be important in the organisation of communities. Studies of nectarivore The work presented in this thesis aimed to do the communities suggest a number of ways in following: which competition causes the component • investigate the cause of decline of the three species to partition resources: size; beak length; Melithreptus species of the Mt Lofty Ranges, habitat; and behaviour, which includes a mix of with a particular emphasis on M. gularis due social and feeding strategies. Due to its role in to its critical status in the ranges; honeyeater community organisation, changed • investigate the ecology and behaviour of level of interspecific competition has been sympatric M. brevirostris and M. lunatus highlighted as a possible cause of decline in populations in the Mt Lofty Ranges; and some honeyeater species in the woodlands of • suggest management options for the three southern Australia. species.

Both interference competition and exploitative Further, it became clear through the course of the competition have been highlighted in various project that an understanding of the decline in situations (Ford et al. 2001). Given the Melithreptus required: hypothesised role of interspecific competition • comparisons with other honeyeater species, in the decline of honeyeater species and the particularly widespread and abundant declining status of all the Melithreptus in the Mt honeyeater species. Lofty Ranges the genus appeared to provide a good basis for examining the hypothesis that Three species of Melithreptus occur in the Mt Lofty interspecific competition is contributing to the Ranges: Brown-headed Honeyeater, Melithreptus decline of some honeyeater species through brevirostris; White-naped Honeyeater, Melithreptus exclusion from resources and/or reduction in lunatus; and Black-chinned Honeyeater, resources available. Melithreptus gularis. Since at least the 1970s all three species have been in decline within the Ford et al. (2001) give the following as potential ranges. One species has been reduced in both tests for their interspecific competition abundance and distribution within the region (M. hypothesis: gularis), while the other two are now recognised • examine community structure for ‘forbidden as having reduced in abundance. December 2015 39

combinations’ (pairs of species that rarely novaehollandiae do prevent M. lunatus from using occur together); certain areas of the landscape. • compare time spent in interspecific competition (interference) and foraging in A final examination of interactions between fragmented and continuous habitat; Melithreptus and widespread and abundant • measure seasonal and spatial patterns of was carried out in the form of a resource abundance and depletion; and survey in which individual trees were watched • remove competitors and observe response in and visits by honeyeater species timed. Based abundance and behaviour of other species. on observations of Melithreptus, it appeared that generally M. brevirostris groups used a swamping These suggestions form the basis for much of the strategy to access defended resources, whereas work presented in this thesis. An initial survey M. lunatus moved quietly, often as individuals or examined not only community structure for pairs. Thus the two species were hypothesised forbidden combinations, but also investigated to use two different behavioural strategies to other possible causes of decline, based on access defended resources, termed stealth (the literature for both declining woodland and use of secretive behaviour to access resources Melithreptus. Besides interspecific competition, that are being protected) and swamping (the use other possible causes included insufficient of a combined direct approach by a number of preferred habitat, insufficient food resources and individuals to access resources that are being landscape fragmentation. protected).

Repeated counts of honeyeaters at 90 sites Based on estimations of the standardised of one hectare in the Mt Lofty Ranges were protection of resources for individual trees, M. undertaken over a one year period. Melithreptus lunatus were able to access defended resources lunatus was found to be more abundant where for longer, while M. brevirostris were able to certain eucalypt species occurred (particularly access better defended resources but for a shorter E. viminalis), although this was postulated to time. These results were consistent with the be a reflection of productive soils. Melithreptus hypothesis of two different behavioural strategies brevirostris was found to be more abundant for accessing defended resources. Both species where Phylidonyris novaehollandiae (New Holland may employ both strategies, but M. brevirostris Honeyeater) was most abundant, despite P. more often use swamping, and M. lunatus more novaehollandiae also being the most widespread often use stealth. and abundant honeyeater in the Mt Lofty Ranges. Thus, the survey work did not find forbidden Investigating the morphology of the small combinations of honeyeaters. However , the honeyeaters of the Mt Lofty Ranges confirmed scale at which the survey work was undertaken that size and beak length were important in (sites of 1 ha) may have masked any competition discriminating between most species. However, between species due to spatial heterogeneity. these did not provide any basis for separating the Melithreptus. Closer examination of morphology At the scale of one hectare there are likely to be between M. brevirostris and the M. lunatus sexes areas of resource not used by other honeyeaters, revealed further similarities to those previously allowing Melithreptus to avoid feeding territories documented. The average values for many of aggressive honeyeaters. Therefore, in order morphological attributes of M. brevirostris fell to more thoroughly investigate competition between the average value for the M. lunatus between P. novaehollandiae and Melithreptus, a sexes, suggesting that ecologically the three removal experiment with finer resolution than species/sexes formed a continuum. The M. lunatus 1 ha was carried out. This demonstrated that P. sexes and M. brevirostris were then referred to as 40 South Australian Ornithologist 41 (1) the small Melithreptus guild (it was not possible to brevirostris and M. lunatus. Melithreptus appear sex M. brevirostris based on the range of attributes to forage predominantly from poor quality measured). The greatest differences between resources, requiring a large proportion of their the small Melithreptus guild were found in wing time allocated to foraging. The small proportion length and leg morphology. The direction of the of time spent resting is probably a result of differences suggested that M. brevirostris would be the time spent foraging. The small proportion more similar to female M. lunatus in movements of time spent in aggression is partly the result and more similar to male M. lunatus in foraging of a lack of aggression by Melithreptus, but behaviour. These two aspects of Melithreptus is also potentially due to their knowledge of ecology were the subject of the last and most aggression levels within their home range and extensive phase of the project. their use of stealth and swamping. Melithreptus are likely to avoid the most highly protected Movements were investigated for Melithreptus (and therefore the most productive) areas within at four sites in the Mt Lofty Ranges using their home ranges. A trend in behavioural data radio-telemetry techniques. Melithreptus were was consistent with the hypothesis that M. found to use large areas of the landscape and brevirostris was more similar to male M. lunatus to have large core areas of activity within than to female M. lunatus. their home range. Using the same methods confirmed that Melithreptus had larger home Based on the data collected in this study, ranges (mean 100% minimum convex polygon Melithreptus in the Mt Lofty Ranges are (MCP) 23 hectares) than P. novaehollandiae characterised by: relatively large home range (mean 100% MCP 5 hectares), and larger home size with core areas that are used over extended ranges than those reported in the literature periods of time; similar foraging behaviour and for other honeyeater species. Data on a single morphology; lack of aggression; and (probably) M. gularis (100% MCP 140 hectares) suggest complex social behaviour. Their decline in that this species has even larger home range the Mt Lofty Ranges can be attributed to the requirements. Information from colour-banded preferential clearance of their preferred habitat, birds suggests that most M. brevirostris and their requirement for a large home range and male M. lunatus had stable core areas of their predominant use of poor quality resources, activity over the period of this study, while particularly in comparison to other, locally female M. lunatus were less likely to have successful honeyeaters. stable core areas of activity, particularly during the non-breeding season. A trend in home The final aim of this work on Melithreptus range and movement data was consistent with honeyeaters in the Mt Lofty Ranges was to the hypothesis that M. brevirostris was more provide options for managing remaining similar to female M. lunatus than to male M. Melithreptus populations, in particular M. gularis lunatus. which, according to informed observers, is now critically endangered in the region. Due to Behaviour of Melithreptus and P. novaehollandiae the extent of habitat clearance in the Mt Lofty were investigated using time budget techniques. Ranges, the decline of Melithreptus will only be Melithreptus were found to spend most of addressed in the long term through large scale their day foraging (up to 84%), very little time revegetation projects. Melithreptus requirements resting (as little as 1.8%) and very little time in any large scale revegetation are most likely to in aggression (as little as 0.6%). These values be met by providing a range of eucalypt species. are each within the outer range of results published on other honeyeaters. Melithreptus In the short to medium term, management gularis behaviour was very similar to both M. actions may be needed to prevent the loss of M. December 2015 41 gularis from the region. Given the findings of REFERENCES this study, there are few such options available. The management of woody weeds in known Ford, H. A., Barrett, G. W., Saunders, D. A. Melithreptus home ranges is suggested as one and Recher, H. F. 2001. Why have birds in the possible management strategy. Melithreptus rarely woodlands of southern Australia declined? use a shrub layer for foraging, shelter or nesting, Biological Conservation 97: 71-88. whereas P. novaehollandiae use a shrub layer Willoughby, N. 2005. Comparative Ecology, and for each of these activities. Thus, where grassy Conservation, of the Melithreptus Genus in the woodlands have been invaded by woody weeds, Southern Mount Lofty Ranges, South Australia. P. novaehollandiae potentially have an increased Ph.D. thesis, University of Adelaide (abstract) year round presence.