Energetics of fattening and starvation in the long-distance migratory garden warbler, Sylvia borin, during the migratory phase

Garden warblers (Sylvia borin) were subjected to starvation trials during their autumnal migratory phase in order to simulate a period of non-stop migration. Before, during and after this treatment the energy expenditure, activity, food intake and body mass of the subjects were monitored. Assimilation efficiency was constant throughout the experiments. The catabolized (during starvation) and deposited body tissue (during recovery) consisted of 73% fat. Basal metabolic rate was decreased during the starvation period and tended to a gradual increase during the recovery period. The reduced basal metabolic rate can possibly be attributed to a reduced size/function of the digestive system, which is consistent with the sub-maximal food intake immediately after resuming the supply of food to the experimental birds. The observed reductions in basal metabolic rate during starvation and activity during recovery can be viewed as adaptations contributing to a higher economization of energy supplies. The experimental birds were unable to eat large quantities of food directly after a period of starvation leading to a comparatively low, or no increase in body mass. Such a slow mass increase is in agreement with observations of migratory birds on arrival at stop-over sites.

Basal metabolic rate, food intake, and body mass in cold- and warm-acclimated Garden Warblers

We address the question of whether physiological flexibility in relation to climate is a general feature of the metabolic properties of birds. We tested this hypothesis in hand-raised Garden Warblers (Sylvia borin), long-distance migrants, which normally do not experience great temperature differences between summer and winter. We maintained two groups of birds under cold and warm conditions for 5 months, during which their body mass and food intake were monitored. When relatedness (siblings vs. non-siblings) of the experimental birds was taken into account, body mass in cold-acclimated birds was higher than in warm-acclimated birds. BMR, measured at the end of the 5-month temperature treatment, was also higher in the cold- than the warm-acclimated group. Migrant birds thus seem to be capable of the same metabolic cold-acclimation response as has been reported in resident birds. The data support the hypothesis that physiological flexibility is a basic trait of the metabolic properties of birds.

Variation in energy intake and basal metabolic rate of a bird migrating in a wind tunnel

1. We studied the changes in body mass, metabolizable energy intake rate (ME) and basal metabolic rate (BMR) of a Thrush Nightingale, Luscinia luscinia, following repeated 12-h migratory flights in a wind tunnel. In total the bird flew for 176 h corresponding to 6300 km. This is the first study where the fuelling phase has been investigated in a bird migrating in captivity.

2. ME was very high, supporting earlier findings that migrating birds have among the highest intake rates known among homeotherms. ME was significantly higher the second day of fuelling, indicating a build-up of the capacity of the digestive tract during the first day of fuelling.

3. Further indications of an increase in size or activity level of metabolically active structures during fuelling come from the short-term variation in BMR, which increased over the 2-day fuelling period with more than 20%, and in almost direct proportion to body mass. However, mass-specific BMR decreased over the season.

4. The patterns of mass change, ME and BMR of our focal bird following two occasions of 12-h fasts were the same as after flights, indicating that fast and flight may involve similar physiological processes.

5. The relatively low ME the first day following a flight may be a contributing factor to the well-known pattern that migrating birds during stopover normally lose mass the first day of fuelling.

High basal metabolic rates of shorebirds while in the Arctic: a circumpolar view

The basal metabolic rate (BMR) of Old World long-distance-migrant shorebirds has been found to vary along their migration route. On average, BMR is highest in the Arctic at the start of fall migration, intermediate at temperate latitudes, and lowest on the tropical wintering grounds. As a test of the generality of this pattern, we measured the BMR of one adult and 44 juvenile shorebirds of 10 species (1-18 individuals of each species, body-mass range 19-94 g) during the first part of their southward migration in the Canadian Arctic (68-76°N). The interspecific relationship between BMR and body mass was almost identical to that found for juvenile shorebirds in the Eurasian Arctic (5 species), although only one species appeared in both data sets. We conclude that high BMR of shorebirds in the Arctic is a circumpolar phenomenon. The most likely explanation is that the high BMR reflects physiological adaptations to low ambient temperatures. Whether the BMR of New World shorebirds drops during southward migration remains to be investigated.

The victories of failure: C. J. Degaris and his Corio garden suburb

Mildura's Clement John De Garis (1884 - 1926) was renowned in his lifetime as an entrepreneur, promoter of Australian literature, publicist, pioneering aviator, author, lyricist, orator, dramatist, irrigationist, newspaper proprietor, magazine editor, land developer and most importantly, a visionary.

'Particularly happy' arrangement?: Idealism, pragmatism and the enclosed open spaces of Perth garden suburbs

One of the hallmarks of many planned garden suburbs of the early twentieth century is the internal reserve: open space at the rear of residences, without street frontage. An idealistic conception with direct links to overseas planning theory, these spaces were not always well received by either local councils or residents; despite this, many survive today as legacies of early suburban reformism. Perth’s highest-profile planning advocates of the interwar years, most notably town clerk William Bold and the progressive surveying  partnership of Hope and Klem, embraced and encouraged the idea and a number of middle-ring suburbs in Perth feature internal reserves which have survived both encroachment and resubdivision. Some have been given heritage status in recognition of their importance to the history and fabric of particular suburban communities; others remain neglected and essentially unacknowledged. All raise ongoing usage, maintenance and management issues for the councils that have inherited them.

Song and female choice for extrapair copulations in the sedge warbler, Acrocephalus schoenobaenus

Although 90% of passerine birds live in socially monogamous pair bonds, molecular studies have revealed that genetic polygamy occurs in 86% of surveyed passerines, because individuals engage in copulations outside the pair bond (extrapair copulations; EPCs). Most explanations for the occurrence of EPCs involve female gaining indirect benefits from the extrapair male. The sedge warbler is a socially monogamous species in which some offspring result from EPCs (8% in this study). Complex song is a sexually selected male trait used by females which select mates based on a variety of male qualities. We used microsatellite DNA profiling to detect extrapair young and assign paternity. ‘Good genes’ theory predicts that females should engage in EPCs with males of higher quality than their social mate, with resulting fitness benefits. Extrapair males had smaller song repertoires and smaller territories than the social mate. This apparent preference for small-repertoire males as extrapair mates conflicts with the predictions from previous studies of this species. Sudden cessation of song after pairing may mean that song cues are unavailable for later extrapair matings and females may switch to other cues. Such behaviour may lead to different patterns of female choice during social and extrapair mating in the sedge warbler. We conclude that multiple reasons underlie patterns of female choice in this species.

Song sharing and repertoire size in the sedge warbler, Acrocephalus schoenobaenus: changes within and between years

The complex song of the male sedge warbler functions mainly in sexual attraction and the evolution of repertoire size is driven primarily by female choice. As male song ceases upon pairing, male–male singing interactions are relatively brief and have not been studied to our knowledge. This study shows that young males in their first breeding season shared significantly more syllables with their nearest neighbour than with their fathers or more distant males. Moreover, daily recordings revealed that rapid learning and modification of syllable repertoires occurred, resulting in a progressive increase in sharing within just a few days. This does not lead to a gradual increase in repertoire size as some syllables are dropped and new ones are acquired. This turnover process allows males to share syllables with their neighbours, whilst repertoire size, known to be important in female choice, remains relatively constant in any one year. Individual males were followed for several years and also showed considerable syllable turnover between years. However, in this case, repertoire size was found to increase between years, the largest increase occurring between the first and second years. We obtained a significant positive correlation between repertoire size and age, suggesting that females choosing males with larger repertoires may gain indirect (genetic) benefits for their offspring, such as good genes for viability. Whilst these results reveal a more flexible picture of repertoire turnover than previously suspected, the relative stability of repertoire size within a season and the increase with age suggests that repertoire size remains a likely target for sexual selection by female choice.

The application of a fuzzy rule based system in an exposition of the antecedents of sedge warbler song flight

The utilization of a fuzzy aspect within data analysis attempts to move from a quantitative to a more qualitative investigative environment. As such, this may allow the more non-quantitative researchers results they can use, based on sets of linguistic terms. In this paper an inductive fuzzy decision tree approach is utilized to construct a fuzzy-rule-based system for the first time in a biological setting. The specific biological problem considered attempts to identify the antecedents (conditions in the fuzzy decision rules) which characterize the length of song flight of the male sedge warbler when attempting to attract a mate. Hence, for a non-quantitative investigator the resultant set of fuzzy rules allows an insight into the linguistic interpretation on the relationship between associated characteristics and the respective song flight duration.

Cultivating health and wellbeing : members' perceptions of the health benefits of a Port Melbourne community garden

This paper reports on a research project undertaken with members of a community garden in Port Melbourne, Australia, to investigate the ways in which such a facility contributes to the enhancement of health, wellbeing and contact with nature for urban dwellers. Ten members from an urban community garden were interviewed using qualitative semi-structured questions exploring perceptions of health and wellbeing benefits associated with membership. The garden was felt by members to be a sanctuary where people could come together and escape daily pressures, a source of advice and social support, and a place which gave them a sense of worth and involvement. Members also identified spiritual, fitness and nutritional benefits arising from participation in the community garden. It is evident even from this small qualitative study that community gardening offers many health and wellbeing benefits to members. This study provides a basis for the benefits of community gardens in Australia to be taken into account by policy-makers and practitioners to enhance urban community health and wellbeing.

Leading lights : the promotion of garden suburb plans and planners in interwar Australia

This thesis explores interwar town planning in Australia, focusing on the period of large-scale urban expansion in the 1920’s. It problematises aspects of Australia’s urban planning history, particularly the 1920s ‘garden suburb. It also investigates the question of the use of international planning ideas in Australia, and the assertion or creation of authority by the Australian planning movement. The thesis additionally investigates the use of authoritative planning rhetoric for commercial or creative advantage. The thesis argues that the majority of innovative planning projects in the interwar years took place in the formation and foundation of the garden suburb. It shows that the garden suburb – assumed in much planning history to be an inferior form of Ebenezer Howard’s ‘garden city’ ideal – has, in fact, a number of precedents in 19th century Australian suburbia, some of which were retained in 20th century commercial estate design. Much of the Australian town planner’s authority at this time required recognition and awareness of the interests and needs of the general public, as negotiated through land vendors. As Australians looked to the future, and to the US for guidance, they were invited to invest in speculative real estate development modelled on this vision. The thesis concentrates primarily on the lives, careers and work of the British-Australian architect-planner Sir John Sulman; the Chicagoan architect-planners Marion Mahony and Walter Burley Griffin; and the Australian surveyor-planner Saxil Tuxen. These individuals were among the most prominent planners in Australia in the interwar years. All designed Australian garden suburbs, and combined advocacy with practice in private and public spheres. The thesis examines images and personas, both generic and individual, of the planner and the vendor. It shows that the formulation of the garden suburb and design practices, and the incorporation of international elements into Australian planning, are important in the creation of planning practice and forms. It also outlines the way these continue to have significant impact, in diverse and important ways, on both the contemporary built environment and planning history itself.

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.

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.