David A. Putland

The importance of functional connectivity in the conservation of a ground-dwelling mammal in an urban Australian landscape

The distribution of the northern brown bandicoot (Isoodon macrourus), a medium-sized ground-dwelling marsupial, was examined in habitat fragments within the urban landscape of the city of Brisbane, Australia. From surveys conducted in 68 fragments, bandicoots were found to be present in 33 (49%) despite widespread habitat loss and fragmentation. Logistic regression analysis revealed that of 13 measured independent variables, functional connectivity was the only factor that significantly predicted the presence of bandicoots within fragments, with connectivity positively correlated with the likelihood of occupation. Functional connectivity was equated to the likelihood of bandicoot immigration into the focal fragment from the nearest occupied fragment, based on the estimated resistance to movement offered by the intervening matrix. Within Brisbane, riparian habitat fragments typically have a relatively high level of functional connectivity, as thin strips of vegetation fringing waterways serve as corridors between larger riparian areas and facilitate the movement of bandicoots between patches. Analyses based on the Akaike Information Criterion revealed that the optimal model based on landscape context variables was convincingly better supported by the data than the optimal model produced from fragment characteristics. However, it is important to examine both internal attributes of habitat fragments and external features of the surrounding landscape when modelling the distribution of ground-dwelling fauna in urban environments, or other landscapes with a highly variable matrix. As urban centres throughout the world expand, it is crucial that the ecology of local wildlife be considered to ensure functional connection is maintained between habitat patches, especially for the conservation of species that are highly susceptible to fragmentation.

Has sexual selection been overlooked in the study of avian helping behaviour

Correspondence: D. Putland, Department of Zoology and Entomology, University of Queensland, St Lucia QLD 4072, Australia (email: dputland@zen.uq.edu.au). Helping behaviour refers to the parental care provided to offspring by individuals that are not the social or genetic parents. The apparent paradox of helping behaviour has been one of the most widely studied areas of behavioural ecology in recent times. Recent reviews (e.g. Koenig & Mumme 1990; Cockburn 1998) have helped to outline the predominant theories in this field, which include the nonadaptive ‘unselected’ hypothesis (Jamieson 1991), and six general classes of adaptive theories: (1) increased production of collateral kin (kin selection); (2) payment-of-rent or mutualism; (3) access to mating opportunities; (4) improvement of local conditions; (5) establishment of strategic alliances (coalitions); and (6) improved skills (from Cockburn 1998). Most research emphasis has been placed on the kinselected benefits of helping, with the result that other benefits of help have yet to be fully explored. One of these other potential benefits gained from helping is increased access to mating opportunities. Helping may improve an individual’s access to mates in many ways. Most obviously, a helper may gain direct benefit if it is able to reproduce within the group. Alternatively, a helper may be able to gain extrapair copulations in neighbouring groups, whereas a nonterritorial floater may not have the same opportunities. Helping could also improve future access to mates; the more dominant helpers may be able to replace (or displace) the primary breeder and assume breeding status (e.g. moustached warbler, Acrocephalus melanopogon: Fessl et al. 1996; bushtit, Psaltriparus minimus: Sloane 1996). In these cases, the improved access to mates follows purely from the individual’s social or geographical position; for example, helping may allow an individual to remain on a higherquality territory than if it dispersed, and from this position, the individual has a better chance of finding a potential mate to court either within or outside of the group. However, what if helping not only improves a helper’s access to mates, but actually attracts mates? I propose that, in some species, helping behaviour may be a

Territorial behaviour in the Tasmanian native hen : group and individual performance

We studied the territorial behaviour of the Tasmanian native hen, Gallinula mortierii, a cooperatively breeding gallinule, for three breeding seasons at Maria Island National Park, Tasmania, Australia. Our analyses of 2738 territorial contests among 54 groups revealed that 87% of interactions were won by the group that initiated the interaction, 7% yielded no clear result, and only 6% were won by the opposing group. Asymmetries in the resource-holding potential of competing groups were not involved in deciding the outcomes of territorial contests. Our results suggest that asymmetries in payoff were involved, as in each of the 3 years groups with better quality territories were more likely to start interactions, and as a result, were more likely to win them. Only 6% of territorial contests escalated to involve physical contact and changes in territory boundaries rarely resulted from individual contests. The quality of a groups territory either changed very little between breeding seasons, or markedly increased or decreased. We conclude that major changes in territory quality occurred only under relatively rare conditions where the risks associated with escalated contests were reduced, or where the payoffs from a favourable result were improved. Males put more effort into the defence of the group territory than did females. The extra effort of males was directed more towards extragroup males than towards extragroup females. Females, in contrast, were equally aggressive towards both sexes. This suggests that the agonistic behaviour of male Tasmanian native hens may contain a mate-guarding component as well as functioning in the defence of territory. (c) 1998 The Association for the Study of Animal Behaviour.

Imitating the neighbours: vocal dialect matching in a mimic-model system

Vocal mimicry provides a unique system for investigating song learning and cultural evolution in birds. Male lyrebirds produce complex vocal displays that include extensive and accurate mimicry of many other bird species. We recorded and analysed the songs of the Alberts lyrebird (Menura alberti) and its most commonly imitated model species, the satin bowerbird (Ptilonorhynchus violaceus), at six sites in southeast Queensland, Australia. We show that each population of lyrebirds faithfully reproduces the song of the local population of bowerbirds. Within a population, lyrebirds show less variation in song structure than the available variation in the songs of the models. These results provide the first quantitative evidence for dialect matching in the songs of two species that have no direct ecological relationship.

Geographic variation in vocalisations of Satin Bowerbirds, Ptilonorynchus violaceus, in south-eastern Queensland

Abstract Geographic variation in the advertisement call of the male Satin Bowerbird, Ptilonorhynchus violaceus, was investigated in three populations in south-eastern Queensland. The call was found to differ significantly among the three geographically distinct populations. A discriminant function analysis using five measurements of call frequency and duration provided 100% classification success of the 25 individuals. The observed geographic variation in this call may result from adaptation to the local acoustic environment in these populations, or from genetic or cultural divergence among populations. Further research involving the acoustic properties of the habitats, population genetics and a larger number of populations is required to fully understand this pattern of call variation.

Effects of habitat characteristics and climate on the distribution and colouration of Dusky Moorhens (Gallinula tenebrosa) in south-east Queensland

Abstract We determined which factors predict the presence and abundance of Dusky Moorhens (Gallinula tenebrosa) at wetlands by surveying the ecological and habitat characteristics of 62 sites across south-east Queensland. Moorhens were observed in 48 of the sites sampled. They were more likely to be found at sites surrounded by taller terrestrial vegetation and where free-floating and attached aquatic vegetation was more abundant. The number of moorhens found at a site increased in relation to vegetation height, the abundance of attached aquatic vegetation and the number of purple swamphens observed. These results suggest that there are ecological constraints on the distribution of moorhens, and that food abundance and the availability of suitable nesting sites determine the overall distribution and abundance of moorhens in wetlands. Adult moorhens develop brightly coloured fleshy frontal shields, bills and legs when breeding, although in some populations birds maintain year-round colouration. We observed year-round breeding colouration in 23 out of 34 sampling sites that had moorhens and were surveyed in August. Coloured moorhens were found during winter at sites with higher minimum winter temperatures, and more abundant free-floating and submerged leafy vegetation. In addition, higher proportions of moorhens were coloured at sites with higher mean minimum temperatures. The retention of year-round breeding colouration appears to be restricted to areas with warmer winter temperatures and more abundant food. The results suggest that areas not occupied by moorhens are of inadequate quality to support breeding populations. We suggest that ecological constraints on independent breeding in Dusky Moorhens may have favoured the evolution of their unusual cooperative breeding system, which involves frequent mate-sharing by both sexes.

Juvenile helping behaviour in the Dusky Moorhen, Gallinula tenebrosa

Abstract In Dusky Moorhens, Gallinula tenebrosa, helping behaviour may be displayed by juveniles when groups contain offspring of different age classes. We investigated the frequency and amount of parental care provided by juvenile moorhens to younger siblings from subsequent same-year broods. In some social groups, juveniles provided up to 33% of the total number of feeds provided to chicks. Juveniles were observed to feed chicks when as young as six weeks of age, often while still receiving food from adults themselves. Low within-group relatedness and low reproductive costs associated with juvenile helping have important consequences for the cost-benefit ratio of helping behaviour in this species.