Parasites affect song complexity and neural development in a songbird

There is now considerable evidence that female choice drives the evolution of song complexity in many songbird species. However, the underlying basis for such choice remains controversial. The developmental stress hypothesis suggests that early developmental conditions can mediate adult song complexity by perturbing investment in the underlying brain nuclei during their initial growth. Here, we show that adult male canaries (Serinus canaria), infected with malaria (Plasmodium relictum) as juveniles, develop simpler songs as adults compared to uninfected individuals, and exhibit reduced development of the high vocal centre (HVC) song nucleus in the brain. Our results show how developmental stress not only affects the expression of a sexually selected male trait, but also the structure of the underlying song control pathway in the brain, providing a direct link between brain and behaviour. This novel experimental evidence tests both proximate and ultimate reasons for the evolution of complex songs and supports the Hamilton–Zuk hypothesis of parasite-mediated sexual selection. Together, these results propose how developmental costs may help to explain the evolution of honest advertising in the complex songs of birds.

Developmental stress, social rank and song complexity in the European starling (Sturnus vulgaris)

Bird song is a sexually selected trait and females have been shown to prefer males that sing more complex songs. However, for repertoire size to be an honest signal of male quality it must be associated with some form of cost. This experiment investigates the effects of food restriction and social status during development on song complexity in the European starling (Sturnus vulgaris). Birds that experienced an unpredictable food supply early in life produced a significantly smaller repertoire of song phrases than those with a constant food supply. Social status during development was also significantly correlated with repertoire size, with dominant birds producing more phrase types. This study therefore provides novel evidence that social as well as nutritional history may be important in shaping the song signal in this species.

Developmental stress affects the attractiveness of male song and female choice in the zebra finch (Taeniopygia guttata)

Developmental stress has recently been shown to have adverse effects upon adult male song structure in birds, which may well act as an honest signal of male quality to discriminating females. However, it still remains to be shown if females can discriminate between the songs of stressed and non-stressed males. Here we use a novel experimental design using an active choice paradigm to investigate preferences in captive female zebra finches (Taeniopygia guttata). Nine females were exposed to ten pairs of songs by previously stressed and non-stressed birds that had learned their song from the same tutor. Song pairs differed significantly in terms of song complexity, with songs of stressed males exhibiting lower numbers of syllables and fewer different syllables in a phrase. Song rate and peak frequency did not differ between stressed and non-stressed males. Females showed a significant preference for non-stressed songs in terms of directed perching activity and time spent on perches. Our results therefore indicate that developmental stress affects not only the structure of male song, but that such structural differences are biologically relevant to female mate choice decisions.

Economic transition and commercial property cycles in China

Drawn from a recently completed study, this paper aims at a better understanding of commercial property cycles in the transitional economy of China. It examines the behaviour of the property submarket system in China and considers structural changes in the socio-economic system as a primary factor in addressing the research problem. The study suggests that the underlying social and economic structure has greatly determined market behaviour. It finds that radical changes can alter the formal structure (the designed structure) of the market system, including the property market structure, but cannot alter the informal structure (i.e. the emergent structure) at the similar rate. As the study shows, cycles in the commercial property market in the economic transition is largely a key resulting feature of the continuous structural change both at formal and informal levels in a way that is often imbalanced and not always consistently changing together. The same situation also applies to the transformation of inner-city built form, which is featured by a delayed change of physical building stock against the space demand trend that is underpinned by the socio-economic transition. Put simply, there is a supply lag, mainly in the form of changing land use and building stock replacement, against economic change (the business cycle). This affects the level of effective demand for office space and hence becomes a major force in shaping current office cycles.

Understanding property cycles in a residential market

Purpose – This paper aims to review property cycle theory and the relevance of the larger body of knowledge about cycles with reference to the housing market. It also aims to highlight the lack of research into property cycles in the residential sector on a suburb or smaller region basis, as well as the potential for increased knowledge about cycles to assist to avoid housing stress.

Design/methodology/approach – The paper conducts a literature review of previous cycle research and encourages the use of cycle theory. It discusses the established body of knowledge about business cycles and the office market sector, as well as investigating levels of housing affordability and how detailed knowledge about property cycles can assist to decrease housing affordability in residential areas, which will eventually experience a downturn.

Findings – It is argued that an increased level of certainty about cycle behaviour in particular suburbs will give households a higher level of confidence when considering whether and when to enter the market. Property cycle research has the potential to assist low-income homeowners to better understand the characteristics of cycles and associated risks in each residential.

Research limitations/implications – This is a conceptual paper and has conducted a review of cycle research and housing affordability in certain countries. Some areas or countries may be affected to varying degrees by property cycles and levels of housing affordability.

Practical implications – In extended periods of high volatility it is argued that a better understanding of housing cycles will allow more homeowners to avoid negative equity and the stress associated with repossessions. Property cycles are unavoidable although there is typically relatively little information available in the open market about the timing and amplitude of cycles in individual areas.

Originality/value – This paper is unique as it highlights the potential for property cycles to be used to avoid housing stress in the residential market. Traditionally cycle research is used to increase returns and avoid downturns in the office and/or business sectors.

Cycles of genocide, stories of denial : Atom Egoyan's Ararat

This article focuses on Atom Egoyan's Ararat and explores how, through a convoluted narrative structure, Egoyan grapples with denial of the Armenian Genocide and the consequences of those denials for present generations—both Turkish and Armenian—illuminated in the film as an extension of the genocide. Egoyan uses a film-within-a-film to move beyond a popular definition of genocide as mass killing alone and links the understanding of stories, truths, and perspectives in everyday life to the dehumanizing acts of genocide. Employing the philosopher Emmanuel Levinas’ ethical theory of the Other (the ethical) and philosophical understandings of ontology (dehumanization) to illuminate the genocide and its ongoing denial, this article contends that Egoyan's focus on the generations of genocide survivors points to the ethical responsibility to one another that underlies everyday lives and sits at the heart of what is absent in the acts of genocide.

Singing as a handicap : the effects of food availability and weather on song output in the Australian reed warbler Acrocephalus australis

Bird song is generally regarded as a sexually selected trait, and may represent a reliable handicap signal under at least certain conditions. Females may use the degree of male song production as a reliable cue to male condition or territory quality. We investigated the effect of supplementary feeding on song output in the migratory Australian reed warbler Acrocephalus australis. We experimentally increased the food availability on alternate days, and recorded several weather variables. We measured song rate and song length independently. Supplementary fed birds sang more on feeding days than on non-feeding days, while control birds did not show this effect. Song output was not significantly associated with any of the weather variables examined. Our results indicate that singing has the potential to serve as a reliable handicap signal to territorial food availability irrespective of the prevailing weather conditions. We discuss the role of energetic constraints and behavioural flexibility on the signaling function of song.

Owl song : a study in tragedy

The thesis is a creative work with exegesis. The creative component is a playscript exploring European tragic form within a mythologised Australian context. The exegesis examines the research material that informed the playwriting process; including tragic theory, dramatic character, place and landscape, and the use of landscape in theatre.

Are business cycles stationary fluctuations around a deterministic trend? empirical evidence from 79 developing countries

There is a large literature that tests the univariate time series properties of the real output series following the seminal work of Nelson and Plosser (1982). Whether or not real output is characterized by a unit root process has important implications. A unit root in real output, for instance, is inconsistent with the notion that business cycles are stationary fluctuations around a deterministic trend. In this paper, we investigate the univariate time series properties of real output for 79 developing countries using the conventional augmented Dickey and Fuller (1979) unit root test, the Zivot and Andrews’ (1992) one structural break unit root test, and the Lumsdaine and Papell (1997) two structural breaks unit root test. Our main finding is that, for 40 countries, real output is stationary around a trend. This indicates that business cycles are stationary fluctuations around a deterministic trend for only 51% of the developing countries in our sample.