Attacks on humans by Australian Magpies (Cracticus tibicen): Territoriality, brood-defence or testosterone?

Attacks on humans by Australian Magpies (Cracticus tibicen) are a significant human-wildlife conflict in Australia, especially in suburban environments. Remarkably little is known about the phenomenon. In this study, we explored three common hypotheses - territoriality, brood-defence and testosterone - as potential and non-exclusive explanations for aggression directed at people by Magpies living in suburban areas of Brisbane, south-eastern Queensland. The response of 10 pairs of aggressive Magpies to natural levels of human intrusion was compared with that of 10 non-aggressive pairs. Behavioural observations strongly supported the contention that attacks on humans resemble brood-defence and did not support an association with territoriality. The study also found no support for the suggestion that testosterone levels correlated with aggressiveness towards humans: male testosterone peaked immediately before laying and was significantly lower during the maximum period of attacks directed at people. Moreover, there were no differences in the testosterone levels of aggressive and non-aggressive male Magpies. The pattern of testosterone production over a breeding cycle closely resembled that of many other songbirds and appeared not to influence Magpie attacks on humans. © Royal Australasian Ornithologists Union 2010.

Beach-foraging behaviour of Forest Ravens Corvus tasmanicus and an Australian Magpie Gymnorhina tibicen at Wilsons Promontory, Victoria

Observations are presented of Forest Ravens Corvus tasmanicus, and an Australian Magpie Gymnorhina tibicen, foraging by gleaning the sand on a beach.

Climatic variation and breeding in the Australian magpie (Gymnorhina Tibicen) : a case study using existing data

To anticipate the effects of climate change on Australia’s avifauna, it is first necessary to understand the current effects of climate (including climate variability) on life histories, and to examine the scope and nature of existing data that may provide the necessary historical context to anticipate the effects of climate change. This study examines naturally occurring geographical gradients (altitude, latitude) and the Southern Oscillation Index (SOI) as integrated measures of climate. These are then compared with the timing and ‘amount’ of breeding recorded for the Australian Magpie (Gymnorhina tibicen) using data from Birds Australia’s Nest Record Scheme and Atlas of Australian Birds, the NSW Bird Atlassers Inc.’s NSW Bird Atlas, and the Canberra Ornitholgists Group’s Garden Bird Survey. For this common, easily identified species, these data suggest links between Australian Magpie breeding and all three environmental variables. Breeding became later as altitude increased, the proportion of breeding records increased from north to south, and years of high SOI corresponded to more (and earlier) breeding in this species. That annual climatic fluctuations have a direct, immediate and substantial effect on breeding in the Australian Magpie, particularly on the amount of breeding that occurs, implies that longer term changes in climate will have substantial impacts on populations. Results were not solely temperature-driven, which makes predicting climate change impacts difficult. For rainfall, predictions are far less precise and regional variation is higher. The results also highlight the potential and limitations of current survey techniques for documenting the impacts of climate change on birds; in particular, the Nest Record Scheme does not measure the amount of breeding that occurs, but a useful index of this can be derived from bird atlassing data

Sperm competition and offspring viability at hybridization in Australian tree frogs, Litoria peronii and L. tyleri

Hybridization between closely related species often leads to reduced viability or fertility of offspring. Complete failure of hybrid offspring (post-zygotic hybrid incompatibilities) may have an important role in maintaining the integrity of reproductive barriers between closely related species. We show elsewhere that in Peron's tree frog, Litoria peronii, males more closely related to a female sire more offspring in sperm competition with a less related rival male. Observations of rare 'phenotypic intermediate' males between L. peronii and the closely related L. tyleri made us suggest that these relatedness effects on siring success may be because of selection arising from risks of costly hybridization between the two species. Here, we test this hypothesis in an extensive sperm competition experiment, which shows that there is no effect of species identity on probability of fertilization in sperm competition trials controlling for sperm concentration and sperm viability. Instead, there was a close agreement between a male's siring success in isolation with a female and his siring success with the same female in competition with a rival male regardless of species identity. Offspring viability and survival, however, were strongly influenced by species identity. Over a 14-day period, hybrid offspring suffered increasing mortality and developed more malformations and an obvious inability to swim and right themselves, leading to compromised probability of survival. Thus, hybridization in these sympatric tree frogs does not compromise fertilization but has a strong impact on offspring viability and opportunity for reinforcement selection on mate choice for conspecific partners.

Multilocus phylogeography of Australian teals (Anas spp.) : a case study of the relationship between vagility and genetic structure

Biogeographic barriers potentially restrict gene flow but variation in dispersal or vagility can influence the effectiveness of these barriers among different species and produce characteristic patterns of population genetic structure. The objective of this study was to investigate interspecific and intraspecific genetic structure in two closely related species that differ in several life-history characteristics. The grey teal Anas gracilis is geographically widespread throughout Australia with a distribution that crosses several recognized biogeographic barriers. This species has high vagility as its extensive movements track broad-scale patterns in rainfall. In contrast, the closely related chestnut teal A. castanea is endemic to the mesic southeastern and southwestern regions of Australia and is more sedentary. We hypothesized that these differences in life-history characteristics would result in more pronounced population structuring in the chestnut teal. We sequenced five nuclear loci (nuDNA) for 49 grey teal and 23 chestnut teal and compared results to published mitochondrial DNA (mtDNA) sequences. We used analysis of molecular variance to examine population structure, and applied coalescent based approaches to estimate demographic parameters. As predicted, chestnut teal were more strongly structured at both mtDNA and nuDNA (ΦST= 0.163 and 0.054, respectively) than were grey teal (ΦST < 0.0001 for both sets of loci). Surprisingly, a greater proportion of the total genetic variation was partitioned among populations within species (ΦSC= 0.014 and 0.047 for nuDNA and mtDNA, respectively) than between the two species (ΦCT < 0.0001 for both loci). The ‘Isolation with Migration’ coalescent model suggested a late Pleistocene divergence between the taxa, but remarkably, a deeper divergence between the southeastern and southwestern populations of chestnut teal. We conclude that dispersal potential played a prominent role in the structuring of populations within these species and that divergent selection associated with ecology and life history traits likely contributed to rapid and recent speciation in this pair.

Selection criteria, skill sets and competencies: what is their role in the appointment of vice-chancellors in Australian universities?

Purpose - The research presented here attempts to identify and analyse the reported selection criteria used in the appointment of Australian vice-chancellors (VCs) and to contrast this with the selection criteria actually used. Design/methodology/approach - Contemporary research into the nature, role and purpose of section criteria in appointment processes has chiefly been conducted in the private sector and across various hierarchical levels. The research is based on a PhD entitled "The recruitment and selection of vice-chancellors for Australian universities". The research for the thesis had ethics approval and involved interviews with former and incumbent chancellors, VCs, consultants, representatives of the Australian Vice-Chancellors Committee and selection panel members. Central to this research was the selection criteria and the skill bases selection criteria attempted to measure. A questionnaire was also sent to those listed above. Findings - The findings show that a matching of organisational antecedents with candidate attributes does occur. The research also highlights the key selection criteria used to appoint VCs. It also demonstrates how these key criteria are universally applied but in different orders depending upon the various foci of universities. Non-stated, but important, criteria and competencies are also discussed. Originality/value - No other research exists outlining the skill sets and competencies required by Australian VCs. It is hoped that this research will form the basis for further research and discovery into this field that we know so little about. © Emerald Group Publishing Limited.

Female choice for males with greater fertilization success in the Swedish Moor Frog, Rana arvalis

Background: Studies of mate choice in anuran amphibians have shown female preference for a wide range of male traits despite females gaining no direct resources from males (i.e. non-resource based mating system). Nevertheless, theoretical and empirical studies have shown that females may still gain indirect genetic benefits from choosing males of higher genetic quality and thereby increase their reproductive success.
Methodology/Principal Findings: We investigated two components of sexual selection in the Moor frog (Rana arvalis), precopulatory female choice between two males of different size (‘large’ vs. ‘small’), and their fertilization success in sperm competition and in isolation. Females’ showed no significant preference for male size (13 small and six large male preferences) but associated preferentially with the male that subsequently was the most successful at fertilizing her eggs in isolation. Siring success of males in competitive fertilizations was unrelated to genetic similarity with the female and we detected no effect of sperm viability on fertilization success. There was, however, a strong positive association between a male’s innate fertilization ability with a female and his siring success in sperm competition. We also detected a strong negative effect of a male’s thumb length on his competitive siring success.
Conclusions/Significance: Our results show that females show no preference for male size but are still able to choose males which have greater fertilization success. Genetic similarity and differences in the proportion of viable sperm within a males ejaculate do not appear to affect siring success. These results could be explained through pre- and/or postcopulatory choice for genetic benefits and suggest that females are able to perceive the genetic quality of males, possibly basing their choice on multiple phenotypic male traits.

Short- and long-term consequences of early developmental conditions : a case study on wild and domesticated zebra finches

Divergent selection pressures among populations can result not only in significant differentiation in morphology, physiology and behaviour, but also in how these traits are related to each other, thereby driving the processes of local adaptation and speciation. In the Australian zebra finch, we investigated whether domesticated stock, bred in captivity over tens of generations, differ in their response to a life-history manipulation, compared to birds taken directly from the wild. In a ‘common aviary’ experiment, we thereto experimentally manipulated the environmental conditions experienced by nestlings early in life by means of a brood size manipulation, and subsequently assessed its short- and long-term consequences on growth, ornamentation, immune function and reproduction. As expected, we found that early environmental conditions had a marked effect on both short- and long-term morphological and life-history traits in all birds. However, although there were pronounced differences between wild and domesticated birds with respect to the absolute expression of many of these traits, which are indicative of the different selection pressures wild and domesticated birds were exposed to in the recent past, manipulated rearing conditions affected morphology and ornamentation of wild and domesticated finches in a very similar way. This suggests that despite significant differentiation between wild and domesticated birds, selection has not altered the relationships among traits. Thus, life-history strategies and investment trade-offs may be relatively stable and not easily altered by selection. This is a reassuring finding in the light of the widespread use of domesticated birds in studies of life-history evolution and sexual selection, and suggests that adaptive explanations may be legitimate when referring to captive bird studies.

The spatial pattern of natural selection when selection depends upon experience

Apostatic (frequency‐ or density‐dependent) selection, aposematic signals, and mate choice behavior generally require that the mean prey or potential mate density m value be high enough (above a threshold T) to result in sufficient encounter rates for the searcher to learn or retain the association between conspicuous signals and prey unprofitability, to forage apostatically, or to choose among mates. This assumes that all searchers experience , which implicitly assumes an even dispersion of targets among searcher territories. Uneven dispersion generates new phenomena. If , then only territories with local density x values that are greater than T favor experience‐based behavior, leading to spatially variable frequency‐ or density‐dependent selection intensity. As aggregation increases, the increase in percentage of targets in favorable territories ( ) is greater than the increase in the percentage of territories that are favorable. The relationship is reversed when . In both cases, because as few as 10% of the territories can contain 80% of the targets, only a few territory holders may account for most of the selection on most of the target population; accidents of experience in only a few searchers can have unexpectedly large effects on the target population. This also provides an explanation for high searcher behavior variation (personalities) : individuals from favorable territories will behave differently in behavioral experiments than those from unfavorable territories, at least with respect to similar kinds of targets. These effects will generate spatial heterogeneity in natural and sexual selection in what are otherwise uniform environments.

Environmental variation and the maintenance of polymorphism : the effect of ambient light spectrum on mating behaviour and sexual selection in guppies

The intensity of sexual selection is influenced by environmental conditions because these conditions influence signal propagation and the risks of the signal being exploited by predators and parasites. We explore the possibility that spatial or temporal heterogeneity in environmental signalling conditions (in this case light spectrum) may induce fluctuating sexual selection on male behaviour and ornamentation in guppies. We used shade cloth and filters to experimentally manipulate light spectrum, mimicking conditions found naturally: early morning/late afternoon light (SC treatment), midday forest shade (F89 filter treatment) and midday woodland shade (F55 filter treatment). Females were more responsive to male courtship and males were less likely to attempt sneak copulations under F55 light than the other two treatments. By contrast, male display rate was not influenced by treatment. Females tended to prefer the same males under SC and F55 light, but attractiveness in these treatments was unrelated to attractiveness under F89 light. There were similarities among treatments in the traits that females preferred: females preferred males with larger areas of orange in all three treatments. There were, however, also some differences, including preference for larger males under F89 light and for smaller males under the other treatments. Overall, the influence of ambient light spectrum on the relative importance of mate choice and male sneak copulation may have important implications for the mode and strength of sexual selection in different environments. The findings on attractiveness and preference functions, however, suggest that light spectrum only weakly affects the direction of sexual selection by female choice.

The functional significance of multiple nest-building in the Australian Reed Warbler Acrocephalus australis

The vast majority of bird species build a nest in which to breed. Some species build more than one nest, but the function of most multiple nest-building remains unclear. Here we describe the unusual nest-building behaviour of the Australian Reed Warbler Acrocephalus australis, and test experimentally the hypotheses that multiple nest-building is related to individual condition or territory quality, and plays a role in mate assessment. Australian Reed Warblers built two types of nest structures: 'type I' nests, which were used for eggs and nestlings, and 'type II' nests, which were structurally distinct from type I nests, did not support eggs, nestlings or adults and were not essential for successful breeding. The number of type II nests built in each territory varied. Type II nests were only built before breeding had commenced in a territory and females were not observed participating in their construction, supporting a role in female mate choice. Birds provided with supplementary food built significantly more type II nests than control birds. However, supplementary-fed birds did not have greater pairing success, and the addition of further type II nests to territories did not increase the pairing rate or type II nest construction in those territories. There was no relationship between the presence of type II nests and either reproductive success or likelihood of nest predation. We discuss the implications of these results in light of previous suggestions regarding the function of multiple nest-building in birds.

Is extrapair mating random? On the probability distribution of extrapair young in avian broods

A dichotomy in female extrapair copulation (EPC) behavior, with some females seeking EPC and others not, is inferred if the observed distribution of extrapair young (EPY) over broods differs from a random process on the level of individual offspring (binomial, hypergeometrical, or Poisson). A review of the literature shows such null models are virtually always rejected, with often large effect sizes. We formulate an alternative null model, which assumes that 1) the number of EPC has a random (Poisson) distribution across females (broods) and that 2) the probability for an offspring to be of extrapair origin is zero without any EPC and increases with the number of EPC. Our brood-level model can accommodate the bimodality of both zero and medium rates of EPY typically found in empirical data, and fitting our model to EPY production of 7 passerine bird species shows evidence of a nonrandom distribution of EPY in only 2 species. We therefore argue that 1) dichotomy in extrapair mate choice cannot be inferred only from a significant deviation in the observed distribution of EPY from a random process on the level of offspring and that 2) additional empirical work on testing the contrasting critical predictions from the classic and our alternative null models is required.

An embedded two-layer feature selection approach for microarray data analysis

Feature selection is an important technique in dealing with application problems with large number of variables and limited training samples, such as image processing, combinatorial chemistry, and microarray analysis. Commonly employed feature selection strategies can be divided into filter and wrapper. In this study, we propose an embedded two-layer feature selection approach to combining the advantages of filter and wrapper algorithms while avoiding their drawbacks. The hybrid algorithm, called GAEF (Genetic Algorithm with embedded filter), divides the feature selection process into two stages. In the first stage, Genetic Algorithm (GA) is employed to pre-select features while in the second stage a filter selector is used to further identify a small feature subset for accurate sample classification. Three benchmark microarray datasets are used to evaluate the proposed algorithm. The experimental results suggest that this embedded two-layer feature selection strategy is able to improve the stability of the selection results as well as the sample classification accuracy.

Strategic male signalling effort in a desert-dwelling fish

Males often use elaborate courtship displays to attract females for mating. Much attention, in this regard, has been focused on trying to understand the causes and consequences of signal variation among males. Far less, by contrast, is known about within-individual variation in signal expression and, in particular, the extent to which males may be able to strategically adjust their signalling output to try to maximise their reproductive returns. Here, we experimentally investigated male courtship effort in a fish, the Australian desert goby, Chlamydogobius eremius. When offered a simultaneous choice between a large and a small female, male gobies spent significantly more time associating with, and courting, the former, probably because larger females are also more fecund. Male signalling patterns were also investigated under a sequential choice scenario, with females presented one at a time. When first offered a female, male courtship was not affected by female size. However, males adjusted their courtship effort towards a second female depending on the size of the female encountered previously. In particular, males that were first offered a large female significantly reduced their courtship effort when presented with a subsequent, smaller, female. Our findings suggest that males may be able to respond adaptively to differences in female quality, and strategically adjust their signalling effort accordingly.