bluuebunny/crossref_metadata_2025 huggingface dataset:
Allometric growth, life‐history invariants and population energetics
Authors: Economo Evan P. , Kerkhoff Andrew J. , Enquist Brian J.
Published: March 2005

Population and community level processes must be at least partially determined by variation in the body sizes of constituent individuals, implying quantitative scaling relations can be extended to account for variation in those processes. Here we integrate allometric growth and life‐history invariant theories, and use this approach to develop theory describing the energetics of stationary populations. Our predictions approximate, with no free parameters, the scaling of production/biomass and assimilation/biomass ratios in mammalian populations and work partially for fish populations. This approach appears to be a promising direction and suggests the need for further development of the growth and life‐history models, and extensions of those theories.
Power laws without complexity
Authors: Solow Andrew R.
Published: March 2005

Power laws have been invoked in describing the sizes of a wide variety of objects in evolution and ecology. The apparent ubiquity of power laws is commonly attributed to a form of complex behaviour called self‐organizing criticality. It is shown that power law behaviour inevitably arises from the statistics of large values from heavy‐tailed distributions and that such distributions can be generated by processes that do not involve self‐organized criticality. It follows that power law behaviour cannot be taken as prima facie evidence of self‐organizing criticality.
Big mothers invest more in daughters – reversed sex allocation in a weakly polygynous mammal
Authors: Hewison A. J. Mark , Gaillard Jean‐Michel , Kjellander Petter , Toïgo Carole , Liberg Olof , Delorme Daniel
Published: March 2005

How mothers allocate resources to offspring is central to understanding life history strategies. High quality mothers are predicted to favour investment in sons over daughters when to do so increases inclusive fitness. This is the case in ungulates with polygynous mating systems, where reproductive success is more variable among males than females, but information is scarce on sex allocation in less polygynous species. Here, for the weakly dimorphic roe deer, we show that as maternal capacity to invest increases, mothers increase allocation to daughters more than to sons, so that relative allocation to daughters increases markedly with increasing maternal quality. This cannot be explained by a between sex difference in growth priority, hence we conclude that this is evidence for active maternal discrimination. Further, we demonstrate that condition differences between offspring persist to adulthood. For high quality mothers of weakly polygynous species, daughters may be more valuable than sons.
The Politics of Public–Private Partnerships
Authors: Flinders Matthew
Published: March 2005

Since 1 May 1997 the Labour government in the United Kingdom has implemented a number of public–private partnerships (PPPs) as a central tool of governance within their wider modernisation agenda. To date, the introduction of PPPs has largely been evaluated through conceptual lenses that emphasise either the administrative, managerial, financial or technical dimensions of this reform strategy. This article seeks to complement this wider literature by arguing that PPPs raise a host of political issues and tensions that have largely been overlooked. Five specific themes are set out in order to provide a framework or organising perspective. These are: efficiency; risk; complexity; accountability; and governance and the future of state projects. The main conclusion of the article is that PPPs represent a Faustian bargain in that forms of PPP may deliver efficiency gains and service improvements in some policy areas but these benefits may involve substantial political and democratic costs.
The World Bank, Governance and Theories of Political Action in Africa
Authors: Harrison Graham
Published: March 2005

This article considers the World Bank as a political thinker. This involves an interpretation of the values, methodologies, and theoretical references contained within the Bank's governance documentation. Generally, the Bank steers away from a serious engagement with the nature of states, or the dynamics of reform execution, even in its more detailed policy documents in reform areas such as administrative reform. But, by looking at the World Bank's involvement in African states, we can understand the ways in which the World Bank works with certain expectations concerning how reforms will work. The article critically analyses the Bank's ‘political vision’ by comparing it with prominent theories of African politics. The article concludes that the World Bank's governance agenda misses three pivotal aspects of African politics: the unity of political and economic power, the extreme openness of African states to external pressures, and the salience of historically-embedded cultural and political relations. These three points directly raise important questions about the prospects of good governance reforms in Africa, and the involvement of the Bank therein.
Making Sense of the Globalisation Debate When Engaging in Political Economy Analysis
Authors: Bruff Ian
Published: March 2005

This article assesses various contributions to the globalisation debate. It takes as its basis the split in the political economy literature between three ‘waves’ of analysis, and provides an overview of each in the first part of the article. A progression towards a more sophisticated understanding of ‘globalisation’ has taken place with the emergence of each wave, with the third wave representing the most refined account. The second section suggests neo-Gramscian theory can overcome the shortcomings of the otherwise praiseworthy third wave. In particular, the work of Stuart Hall is presented as appropriate for the study of globalisation, and political economy in general. The article concludes by calling for greater cross-pollination of ideas between the various critical theories of political economy.
Election Forecasting: Principles and Practice
Authors: Lewis-Beck Michael S.
Published: March 2005

To forecast an election means to declare the outcome before it happens. Scientific approaches to election forecasting include polls, political stock markets and statistical models. I review these approaches, with an emphasis on the last, since it offers more lead time. Consideration is given to the history and politics of statistical forecasting models of elections. Rules for evaluating such models are offered. Examples of actual models come from the United States, France and the United Kingdom, where this work is rather new. Compared to other approaches, statistical modelling seems a promising method for forecasting elections.
Forecasting Seats from Votes in British General Elections
Authors: Whiteley Paul F.
Published: March 2005

This article develops a forecasting model of seat shares in the House of Commons applied to general election outcomes. The model utilises past information about party seat shares, together with data from the polls gathered prior to the election, to forecast the number of seats won by the parties. Once it has been estimated the model will be used to make a forecast of the outcome of a possible general election in May 2005. The article starts by focusing on research into translating votes into seats, or the cube rule and its modifications. It then goes on to develop the forecasting model, which is based on electoral and poll data from 1945 to 2001.
Forecasting the 2005 General Election: A Neural Network Approach
Authors: Borisyuk Roman , Borisyuk Galina , Rallings Colin , Thrasher Michael
Published: March 2005

Although neural networks are increasingly used in a variety of disciplines there are few applications in political science. Approaches to electoral forecasting traditionally employ some form of linear regression modelling. By contrast, neural networks offer the opportunity to consider also the non-linear aspects of the process, promising a better performance, efficacy and flexibility. The initial development of this approach preceded the 2001 general election and models correctly predicted a Labour victory. The original data used for training and testing the network were based on the responses of two experts to a set of questions covering each general election held since 1835 up to 1997. To bring the model up to date, 2001 election data were added to the training set and two separate neural networks were trained using the views of our original two experts. To generate a forecast for the forthcoming general election, answers to the same questions about the performance of parties during the current parliament, obtained from a further 35 expert respondents, were offered to the neural networks. Both models, with slightly different probabilities, forecast another Labour victory. Modelling electoral forecasts using neural networks is at an early stage of development but the method is to be adapted to forecast party shares in local council elections. The greater frequency of such elections will offer better opportunities for training and testing the neural networks.
From Aachen to Al‐Andalus: the journey of Deacon Bodo (823–76)
Authors: Riess Frank
Published: March 2005

Sometime in the first six months of 838, Bodo, a palace deacon at the court of Louis the Pious, converted to Judaism, changed his name to Eleazar and removed himself to Muslim Spain. The incident is well attested in various sources although the reasons for his abandonment of Christianity are not clearly given. In 840, a year after arriving in Spain, Bodo, now Eleazar, engaged in a debate with Álvaro of Córdoba, a Christian writer and scholar living in Muslim territory who claimed to be of Jewish ancestry. Their correspondence provides illuminating insights into the framework of cultural and religious experience of this period. Bodo's self‐imposed exile from Christian society is also an important rejection of the Carolingian cultural programme, a voice of protest that was probably more widespread than Carolingian society would have us believe. What follows is partly an analysis of the main textual sources that brings into relief personal, social and political themes seen to lie behind the theolo‐gical debates of the period. There is also an attempt to uncover aspects of Bodo's earlier life before his conversion.
Retinal vascular image analysis as a potential screening tool for cerebrovascular disease: a rationale based on homology between cerebral and retinal microvasculatures
Authors: Patton Niall , Aslam Tariq , MacGillivray Thomas , Pattie Alison , Deary Ian J. , Dhillon Baljean
Published: March 2005

The retinal and cerebral microvasculatures share many morphological and physiological properties. Assessment of the cerebral microvasculature requires highly specialized and expensive techniques. The potential for using non‐invasive clinical assessment of the retinal microvasculature as a marker of the state of the cerebrovasculature offers clear advantages, owing to the ease with which the retinal vasculature can be directly visualizedin vivoand photographed due to its essential two‐dimensional nature. The use of retinal digital image analysis is becoming increasingly common, and offers new techniques to analyse different aspects of retinal vascular topography, including retinal vascular widths, geometrical attributes at vessel bifurcations and vessel tracking. Being predominantly automated and objective, these techniques offer an exciting opportunity to study the potential to identify retinal microvascular abnormalities as markers of cerebrovascular pathology. In this review, we describe the anatomical and physiological homology between the retinal and cerebral microvasculatures. We review the evidence that retinal microvascular changes occur in cerebrovascular disease and review current retinal image analysis tools that may allow us to use different aspects of the retinal microvasculature as potential markers for the state of the cerebral microvasculature.
Relationship of brain and skull in pre‐ and postoperative sagittal synostosis
Authors: Aldridge Kristina , Kane Alex A. , Marsh Jeffrey L. , Yan Peng , Govier Daniel , Richtsmeier Joan T.
Published: March 2005

Models of vertebrate skull evolution stress the coordinated developmental relationship between the skull and the brain that it houses. This study investigates the relationship between altered skull morphology and brain morphology in premature fusion of the cranial sagittal suture (isolated sagittal synostosis; ISS), a condition associated with dysmorphology of both neurocranium and brain. Although the skull displays a more normal shape following reconstructive cranial vault surgery, effects of this surgery on the brain have not been investigated. Landmark coordinate data were collected from three‐dimensional magnetic resonance imaging reconstructions of the brain in a sample of ISS patients and an age‐matched unaffected cohort. These data were analysed using Euclidean distance matrix analysis (EDMA). Results show that the brain in ISS is dysmorphic preoperatively, displaying a posteriorly directed neural expansion that does not ‘worsen’ with growth. Postoperatively, the brain in ISS displays a more globular shape overall as compared with the preoperative morphology, but differs from normal in its subcortical morphology. These results show that the ISS brain is altered following neurocranial surgery, but does not more closely approximate that of unaffected individuals. This suggests that although the brain is affected by manipulation of the skull, it retains a growth pattern that is, at least in part, independent of the skull.
Microvascular patterns in human medullary tegmentum at the level of the area postrema
Authors: Porzionato Andrea , Macchi Veronica , Morsut Leonardo , Parenti Anna , De Caro Raffaele
Published: March 2005

The aim of the present study was to evaluate the regional differences in microvessel density (MVD) of the human medullary tegmentum in adults and newborns/infants. Transverse serial sections of formalin‐fixed, paraffin‐embedded brainstems, taken from 16 adult and eight newborn/infant subjects, were stained with anti‐von Willebrand factor (vWF) polyclonal antibodies. The boundaries of the area postrema (AP), dorsal motor vagal nucleus (DMVN), solitary tract nucleus (STN), solitary tract (ST) and hypoglossal nucleus (XII) were defined, all vessels were counted and the values were divided by the areas. In adult cases, statistically significant heterogeneity in MVD was found among the nuclei studied (P < 0.001). DMVN and AP showed higher MVD with respect to XII and ST (P < 0.001). The MVD of STN was lower with respect to DMVN (P < 0.001) and higher with respect to XII and ST (P < 0.05). The MVD and capillary density of the AP of newborns/infants were not significantly different with respect to adults. In sections of the medulla of adult subjects stained with anti‐vWF, all vessels showed an intense reaction of endothelial cells whereas in the DMVN, XII, STN and ST of newborns/infants, only rare, isolated vessels showed anti‐vWF reactivity and in the AP, 41 ± 21% of vessels expressed vWF. Differences in MVD among the nuclei may be related to their different functions and metabolic demands. Light and heterogeneous expression of vWF in endothelial cells of newborns/infants indicates that differentiation of microvasculature in the human medullary tegmentum extends beyond fetal stages.
Structure and innervation of the tusk pulp in the African elephant (Loxodonta africana)
Authors: Weissengruber G. E. , Egerbacher M. , Forstenpointner G.
Published: March 2005

African elephants (Loxodonta africana) use their tusks for digging, carrying and behavioural display. Their healing ability following traumatic injury is enormous. Pain experience caused by dentin or pulp damage of tusks seems to be negligible in elephants. In this study we examined the pulp tissue and the nerve distribution using histology, electron microscopy and immunhistochemistry. The results demonstrate that the pulp comprises two differently structured regions. Randomly orientated collagen fibres characterize a cone‐like part lying rostral to the foramen apicis dentis. Numerous nerve fibres and Ruffini endings are found within this cone. Rostral to the cone, delicate collagen fibres and large vessels are orientated longitudinally. The rostral two‐thirds of the pulp are highly vascularized, whereas nerve fibres are sparse. Vessel and nerve fibre distribution and the structure of connective tissue possibly play important roles in healing and in the obviously limited pain experience after tusk injuries and pulp alteration. The presence of Ruffini endings is most likely related to the use of tusks as tools.
The structure and innervation of the male urethra: histological and immunohistochemical studies with three‐dimensional reconstruction
Authors: Karam I. , Moudouni S. , Droupy S. , Abd‐Alsamad I. , Uhl J. F. , Delmas V.
Published: March 2005

The structure of the striated urethral sphincter, the so‐called rhabdosphincter, remains the subject of controversy. There are two main concepts regarding its structure: either it is a part of the urogenital diaphragm, or it extends from the base of the bladder up to the urogenital diaphragm and is an integral part of the urethra. It is also uncertain whether it possesses a somatic innervation or a mixed innervation (i.e. autonomic and somatic). The purpose of this study was to show the precise location of the nerves running to the urethra, and to try to determine their exact nature. Histology and immunohistochemistry were performed in the external urethral sphincter of ten male fetuses (114–342 mm crown–rump length, or between 14 and 40 weeks of gestation). A three‐dimensional (3D) reconstruction of the urethral structure and its innervation was made from serial sections. The 3D reconstruction of the same section levels with different strains allowed us to identify the precise structure of the muscle layers (smooth and striated muscle fibres) and the nature of the nerve elements (myelinated and unmyelinated), their distributions and their relationship to the urethral wall, the prostate and the seminal vesicles. Histological and immunohistochemical 3D reconstruction of the anatomical elements of the urethral sphincter helps us to understand the 3D arrangement of the sphincter muscle layers. It also provides a better understanding of the origin and nature of the nerve elements that play a role in urinary continence.
A new fate for old cells: brush cells and related elements
Authors: Sbarbati A. , Osculati F.
Published: March 2005

Over the past 50 years, hundreds of studies have described those cells that are characterized by a brush of rigid apical microvilli with long rootlets, and which are found in the digestive and respiratory apparatuses. These cells have been given names such as brush cells, tuft cells, fibrillovesicular cells, multivesicular cells and caveolated cells. More recently, it has been realized that all these elements may represent a single cell type, probably with a chemosensory role, even if other functions (e.g. secretory or absorptive) seem to be possible. Very recent developments have permitted a partial definition of the chemical code characterizing these elements, revealing the presence of molecules involved in chemoreceptorial cell signalling. A molecular cascade, similar to those characterizing the gustatory epithelium, seems to be present in these elements. These new data suggest that these elements can be considered solitary chemosensory cells with the presence of the apical ‘brush’ as an inconsistent feature. They seem to comprise a diffuse chemosensory system that covers large areas (probably the whole digestive and respiratory apparatuses) with analogies to chemosensory systems described in aquatic vertebrates.
Differences in egg size, shell thickness, pore density, pore diameter and water vapour conductance between first and second eggs of Snares Penguins Eudyptes robustus and their influence on hatching asynchrony
Authors: MASSARO MELANIE , DAVIS LLOYD S.
Published: March 2005

Brood reduction in birds is frequently induced by hatching asynchrony. Crested penguins (genus Eudyptes) are obligate brood reducers, but in contrast to most other birds, first‐laid eggs are considerably smaller in size than second‐laid eggs; furthermore, first‐laid eggs hatch after their siblings. The mechanisms underlying this reversal in size and hatching order remain unclear. In this study, we tested whether the second‐laid eggs of Snares Penguins Eudyptes robustus have a higher eggshell porosity allowing them to maintain a higher metabolic rate throughout incubation and to hatch before their first‐laid siblings. We investigated differences in egg size, shell thickness, pore density, pore diameter and water vapour conductance between first and second eggs within clutches and examined the influence of these shell characteristics on hatching asynchrony. First‐laid eggs of Snares Penguins were approximately 78% of the size of the larger second eggs. Second‐laid eggs had considerably thicker shells and more pores per cm2 than first eggs, whereas pore diameter did not differ between eggs. Water vapour conductance was greater in second‐ (16.8 mg/day/torr) than in first‐laid eggs (14.9 mg/day/torr). The difference in water vapour conductance between first‐ and second‐laid eggs within clutches was related to hatching patterns. In nests where second eggs hatched before first‐laid eggs, second eggs had a considerably greater water conductance than their sibling, whereas in nests where both eggs hatched on the same day, the difference in water conductance between eggs was very small, and in a few nests where small first eggs hatched before their larger sibling, they had a greater water conductance than their larger second‐laid nestmate. Surprisingly few studies have investigated differences in shell characteristics between eggs within clutches and associated effects on hatching asynchrony. This study has demonstrated that such differences exist between eggs within clutches and that they can influence hatching patterns.
Changes in the timing of spring and autumn migration in North American migrant passerines during a period of global warming
Authors: MILLS ALEXANDER M.
Published: March 2005

Butler (2003)used first arrival dates (FADs) of 103 migrant birds in northeastern USA and found that both long‐distance migrants (LDMs; wintering south of the USA) and short‐distance migrants (SDMs; wintering in the southern USA) arrived earlier in the second half of the 20th century than they had in the first, consistent with scenarios of global warming; the trend was stronger in SDMs. Using FADs to characterize migration systems can be problematic because they are data from one tail of a distribution, they comprise a mostly male population and they may not correlate well with the balance of the migration period. FADs also provide no information about autumn migration. This paper uses a banding dataset from Long Point Bird Observatory, Ontario, for 14 passerines for a period of global warming (1975–2000), taking these issues into account. The data were filtered to minimize effects of unequal netting effort (147 491 resulting records), and the passage dates then calculated in each season of each year for the 1st, 2nd and 3rd quartiles for regression analysis. Only two of 13 species analysed in the spring showed significantly earlier passage times, although the overall trend was towards earlier spring migration, especially among SDMs. Autumn responses were more prevalent, however, and in some cases more dramatic with six of 13 species showing delayed migration (four SDMs, two LDMs). Two LDMs exhibited earlier autumn migration. Where earlier spring migration occurred, both sexes appeared to contribute to the change. Where delayed migration occurred in autumn, both sexes and both adults and hatch‐year birds appeared to contribute in at least some cases. The spring FAD results are consistent with those of Butler, but when the whole migration is considered, change is far from universal in spring and is in fact more substantial and complex in autumn.
The scaling of primary flight feather length and mass in relation to wing shape, function and habitat
Authors: DAWSON ALISTAIR
Published: March 2005

The mass and length of each primary flight feather was measured in 120 species of birds (347 individuals) representing 37 families and 15 orders. The scaling relationship between mass and length was determined using the mass of each primary as a proportion of total primary feather mass for that individual and, similarly, length as a proportion of total length. This eliminated errors due to intra‐ and interspecific differences in absolute size. In every species there was a highly significant constant scaling relationship (log mass/log length) for all of the primary feathers proximal to the feather that formed the wing tip. This relationship was allometric and varied between 1.80 in Rooks Corvus frugilegus and 4.87 in Winter Wrens Troglodytes troglodytes. The mean scaling relationship for 120 species was 2.41 ± 0.42 sd, which was significantly less (P < 0.0001) than isometry (i.e. 3.00). In most species (117 of 120) the primary feather forming the wing tip and all feathers distal to it had a different scaling relationship, and had a greater mass than expected from their length. The greater relative mass of the outer primaries may reflect a protective role against physical abrasion, or an aerodynamic role in that each of these feathers provides a leading edge to the wing. Thus, there were two scaling relationships that pivoted about the feather forming the wing tip, resulting in a characteristic ‘signature’ for each species. Scaling relationships can be related to flight characteristics and habitat, rather than to phylogeny. Closely related species often had widely varying scaling relationships. In general, species exploiting dense vegetation had greater scaling relationships than more aerial species. However, species with a high scaling relationship did not have a greater mean feather mass, so the increased relative mass of the distal primaries was at the expense of proximal primary feather mass.
Temporary flightlessness in pre‐laying Common Eiders Somateria mollissima: are females constrained by excessive wing‐loading or by minimal flight muscle ratio?
Authors: GUILLEMETTE MAGELLA , OUELLET JEAN‐FRANÇOIS
Published: March 2005

Large body size, small wings and relatively low flight muscle mass are general attributes of flightlessness in birds, but a general analysis is lacking when considering these factors simultaneously. Common Eiders Somateria mollissima are large sea ducks characterized by short, pointed wings of low surface area. Because females fast throughout incubation, they need to accumulate large body reserves prior to laying. During this pre‐laying period, many females cannot take off, and dive when approached under still‐air conditions, whereas males take off readily when disturbed. In this paper, we examine how pre‐laying female Common Eiders fit the maximum wing‐loading ratio of Meunier, the marginal flight muscle ratio (FMR) of Marden and predictions of a general model of take‐off performance (also by Marden). Wing morphology was recorded and flight muscles were dissected from specimens collected during the pre‐laying period near one breeding colony. In addition, take‐off ability, as observed during collection, was compared with the proposed thresholds for flightlessness and outputs from the general model of take‐off performance. The results indicated that half of the pre‐laying females exceeded the wing‐loading ratio of Meunier, although all females had values above 0.160, the flight muscle ratio below which take‐off would be impossible. We suggest that wing‐loading and flight muscle ratio interact in Eiders, with higher FMR compensating for excessive wing‐loading. Nevertheless, the model of take‐off performance predicted, with reasonable accuracy, the behavioural observations under still‐air conditions. Indeed, females that were predicted to be temporarily flightless could produce a specific lift of 8.8 N/kg on average (less than the 9.8 N/kg required to overcome gravity). In contrast, the average specific lift predicted for males capable of flight was estimated to be 11.4 N/kg. These results agree with our observations that female Common Eiders are at the limit of flight capability in vertebrates.
Temporary flightlessness as a potential cost of reproduction in pre‐laying Common EidersSomateria mollissima
Authors: GUILLEMETTE MAGELLA , OUELLET JEAN‐FRANÇOIS
Published: March 2005

The rapid growth and reabsorption of the avian ovary is thought to be adaptive, as it reduces predation risk and the metabolic cost of flight. In this paper, we use an extreme case of parental investment to show how the survival of gravid birds may be impaired by reduced take‐off ability. In still air, temporary flightlessness is regularly observed in female Common EidersSomateria mollissimapreparing for breeding. From a sample of pre‐laying females collected in the Baltic Sea, we quantified the relationships among body reserves, organ mass and take‐off ability using a general model of take‐off performance. Average body mass at the beginning and end of follicular growth was, respectively, 32% and 43% higher than winter body mass. Wing‐loading increased significantly during ovary development whereas the relative mass of flight muscles decreased. In contrast, organ mass and somatic body mass were constant from early follicular growth until laying, indicating that the observed increase in body mass was caused by ovary growth. The average specific lift production of individuals collected at the beginning of follicular growth was 9.7 N/kg, which is similar to the lift required to become airborne (9.8 N/kg). As ovary mass increased, lift production decreased to 9.2 N/kg at the onset of laying. These results indicate that temporary flightlessness results from the accumulation of large body reserves and subsequent ovarian growth. Predators of Common Eiders are diverse and may come from air, water and land. We suggest that temporary flightlessness may decrease adult survival through predation, and may represent an important cost of reproduction.
Reversed sexual size dimorphism and parental care in the Red‐footed Booby Sula sula
Authors: LORMEE HERVE , BARBRAUD CHRISTOPHE , CHASTEL OLIVIER
Published: March 2005

The ‘division‐of‐labour’ hypothesis predicts that males and females perform different roles in parental care and that natural selection acts differently on each sex so as to produce different body size optima suited to their particular roles. Reversed sexual size dimorphism in avian species (females larger than males) may therefore be an adaptive consequence of different roles of males and females in parental care. We investigated patterns of nest attendance, brooding, foraging and provisioning rate in a tropical seabird, the Red‐footed Booby Sula sula, a species showing a reversed sexual size dimorphism. During incubation, females attended the nest more often than males, and spent more time brooding the small chick than did males during daytime. Males and females did not differ in the average duration of their foraging trips. During incubation, there was a positive relationship between nest attendance and the duration of foraging trips in males, but not in females. During the small‐chick stage, for the same time spent at the nest, males spent significantly more time than females at sea. On average, females fed the chick more often than did males. In males, there was a significant and positive relationship between the probability of feeding the chick and the duration of the foraging trip, whereas in females, this probability was much less dependent on the duration of the foraging trip. Overall, female Red‐footed Boobies achieved slightly, but significantly, more parental commitment than did males. However, these sexual differences in parental participation were small, suggesting a minimal division of labour in the Red‐footed Booby. Our results suggest that the division of labour hypothesis is unlikely to explain fully the adult size dimorphism in Red‐footed Boobies.
Reproductive performance changes with age and laying experience in the Red‐legged Partridge Alectoris rufa
Authors: CABEZAS‐DÍAZ SARA , VIRGÓS EMILIO , VILLAFUERTE RAFAEL
Published: March 2005

Most studies of birds have reported positive effects of ageing on reproductive traits during the first years of life followed by a decline. We examined the effects of age and laying experience, controlling for confounding factors such as food availability/quality and timing of pair formation in a captive population of Red‐legged Partridge Alectoris rufa. We found that all reproductive traits, except for the period between eggs, were highly repeatable within females both within and between years. The repeatability of egg mass was lower than that of clutch size, laying onset or chick traits other than the mass and size increase rates, perhaps suggesting a lower heritability value. As females aged, they showed a tendency to produce marginally lighter eggs (1.3%) and larger clutches, although this latter trend was not significant. We suggest that the senescence process implies the involvement of hormonal changes that could affect the reduction of egg mass (e.g. low levels of oestradiol). Younger females tended to start laying later than older females, which could be due to a low responsiveness to photoperiodic stimulation of the reproductive system, which would indicate a delay in gametogenesis and steroidogenesis. The mass of last‐laid eggs decreased with age of the female. We suggest that physiological changes through the laying sequence could vary with age. Experienced breeders laid larger clutches linked with the advancement of laying onset. For a given age, females with more experience fared better than those with less experience.
First Guyana records, natural history and systematics of the White‐naped Seedeater Dolospingus fringilloides
Authors: ROBBINS MARK B. , BRAUN MICHAEL J. , HUDDLESTON CHRISTOPHER J. , FINCH DAVIS W. , MILENSKY CHRISTOPHER M.
Published: March 2005

We report the first records of the White‐naped Seedeater Dolospingus fringilloides for Guyana, provide new information on its natural history and plumage sequences, and clarify its systematic relationships based on DNA sequence data. Dolospingus is a rare and patchily distributed endemic of white‐sand scrub of the Guianan shield region. Phylogenetic analyses of a broad sampling of emberizine cytochrome b sequences identified a ‘seed finch’ clade consisting of the genera Sporophila, Oryzoborus and Dolospingus with 100% bootstrap support. More intensive maximum‐likelihood (ML) and Bayesian analyses conducted with a reduced data set indicated strong support for the same ‘seed finch’ clade, but could not distinguish the three genera. In the optimal ML trees, Dolospingus and Oryzoborus were nested within Sporophila, and the two Oryzoborus sequences did not cluster together. However, resolution within the seed‐finch clade was weak, so the possibility that all three genera are monophyletic cannot be excluded on the basis of the available molecular data. Thus, whether to group these genera on the basis of genetic similarity or retain them on the basis of diagnostic bill and skull differences will remain a matter of preference until a more fully resolved phylogeny of the seed‐finch clade is achieved.
Night‐time behaviour of egg‐laying tits
Authors: PENDLEBURY C. J. , BRYANT D. M.
Published: March 2005

We provide evidence that nestbox‐breeding tits roost in their boxes at night during the egg‐laying period, but are able to do so while avoiding initiating incubation, despite choosing to settle into the nest‐cup. Nest‐cup temperatures of Great Tits Parus major, during the egg‐laying period, were usually below the threshold for embryo development. This suggests an ability to control heat transfer to the eggs in spite of the close proximity of the female to her clutch. We suggest that an important benefit of roosting in the nest‐cup during the egg‐laying period is reduced thermoregulatory costs, which may be important in moderating the energetic costs of egg production. Another possible advantage is that developmental abnormalities associated with egg‐chilling are avoided.
Of squeezers and skippers: factors determining the age at moult of immature African Penguins Spheniscus demersus in Namibia
Authors: KEMPER JESSICA , ROUX JEAN‐PAUL
Published: March 2005

We used banding and resighting records of 391 African Penguins Spheniscus demersus banded as chicks and later resighted during immature moult to explain the roles of date of fledging and age at moult in determining the season of moult and its timing within the season. Breeding was continuous, but immature moult occurred mainly during spring and summer. Age at immature moult extended over 11 months, from 12 to 23 months after hatching. Birds that fledged during summer and early autumn generally moulted during the next moult season (squeezers), whereas birds that fledged in late autumn, winter and spring skipped the next moult season to moult only the following season (skippers). There was a significant relationship between age at moult and moult date, with young birds moulting later in the season than older birds. The age at moult of immature birds appears to be constrained by minimum age, moult seasonality and plumage wear. Birds that fledged over nearly 2 years moult during one season. Counts of moulting immature African Penguins have not been used to estimate year‐class strength and post‐fledging survival owing to the wide range of ages at immature moult. Our results provide the means of assigning recruits to specific age groups.
At‐sea distributions and abundance of tropicbirds in the eastern Pacific
Authors: SPEAR LARRY B. , AINLEY DAVID G.
Published: March 2005

During spring and autumn 1980–95, we surveyed Red‐tailedPhaethon rubricauda, White‐tailedP. lepturusand Red‐billed TropicbirdsP. aethereusat sea in the Pacific between the coast of the Americas and 176°W. For the Pacific, we had complete coverage of the range ofaethereus, but only partial coverage of that ofrubricaudaandlepturus. Six areas of higher density were indicated: three ofrubricauda, two oflepturusand one ofaethereus. After pooling data across years, the ‘abundance’ (total number including subadults and adults) estimate forrubricaudawas 81 700 (boreal spring) and 86 500 (boreal autumn) birds. Abundance of each of the threerubricaudasubpopulations differed between seasons by about 50% despite seasonal consistency when populations were grouped. Furthermore, high densities ofrubricaudaoccurred at the edge of our study area, indicating that neither of the seasonal estimates for this species could be considered as total numbers. Abundance estimates oflepturusduring the non‐breeding season (when these birds had dispersed from colonies) were 11 000 and 41 500 birds for northern and southern populations, respectively. Estimated abundance ofaethereusduring the boreal spring was 26 700 birds, and 33 400 during the boreal autumn. Because tropicbirds are attracted to survey vessels, we also estimated the abundance after excluding those recorded as flying in a steady direction, or having been attracted to the ship. Considering only stationary birds (i.e. those that could not have been attracted), our minimum estimates were 41 000rubricauda, 15 750aethereus, 28 000 southernlepturusand 6400 northernlepturus.
Population size and trends of the Galápagos Penguin Spheniscus mendiculus
Authors: VARGAS HERNÁN , LOUGHEED CECILIA , SNELL HOWARD
Published: March 2005

We applied a capture–mark–resight (CMR) method to estimate the population size of the Galápagos Penguin Spheniscus mendiculus. In 1999, we estimated 1198 individuals, with lower and upper 95% confidence limits of 1054 and 1403 individuals, respectively, and estimated that approximately 57% of the total population was counted in an annual census. Applying this estimate to the 2003 census, we estimated that the population size for the whole archipelago was 1351 individuals. We also applied the correction factor derived from the 1999 CMR data to other censuses carried out between 1970 and 2003 and estimated a maximum population of about 4000 individuals in 1971 when the highest numbers of Penguins were counted. Although the Penguin population size has fluctuated in the last 33 years, the overall trend shows larger populations in 1970–80 followed by relatively smaller populations and a slow recovery rate in 1983–2003. The data set also shows two major population declines (in 1983 and 1998), which are coincident with El Niño episodes.
Sex‐differences in nest defence in Fieldfares Turdus pilaris in relation to their size and physical condition
Authors: HOGSTAD OLAV
Published: March 2005

The nest defence of solitary‐breeding Fieldfares Turdus pilaris against a human intruder, a corvid and a hawk was studied in a mountain birch forest in central Norway in 1990–2002. Females defended their nests against a human intruder more vigorously than did males before hatching, and vice versa after hatching. Although both sexes increased their nest defence, only males showed a significant increase and showed a greater defence than females at the chick stage. Females with 1‐week‐old nestlings had longer wings, were heavier and in a better physical condition than those that failed to get nestlings to that stage. Females, but not males, lost condition during nesting. Birds in better condition were more aggressive. The pattern of nest defence by males and females against the corvid was similar to that shown against human intruders, whereas males took greater risks than females towards the raptor. There was weak evidence that birds that were more successful showed greater levels of nest defence. The sex‐role reversal in nest defence may be connected to differences in costs in relation to the renesting potential and to the physical condition of the sexes.
Colony size, reproductive success, and colony choice in Cave Swallows Petrochelidon fulva
Authors: WEAVER HEATH B. , BROWN CHARLES R.
Published: March 2005

We investigated how annual reproductive success, as measured by the number of nestlings surviving to day 10 and the percentage of nests that were successful, varied with colony size of the Cave Swallow Petrochelidon fulva in south central Texas. We also studied whether Cave Swallows chose colonies, in part, on the basis of reproductive success at a site the previous year. Neither measure of reproductive success varied significantly with colony size for either first‐wave or second‐wave nestings. Mean clutch size per colony did not vary significantly with colony size. Mean nestling body mass, an index of parental foraging efficiency, was unrelated to colony size, except for broods of five, in which nestling mass declined significantly with colony size. Colony size was not significantly affected by reproductive success at the site the previous year, although sites with more successful nests during the first wave declined less in size during the second wave within the same season than did sites that had fewer successful first‐wave nests. Unlike the closely related Cliff Swallow Petrochelidon pyrrhonota, Cave Swallows did not use breeding performance of conspecifics in choosing nest‐sites, because they did not preferentially aggregate at sites that were the most successful the previous year. Coloniality in Cave Swallows did not appear to have a net negative effect on annual fitness, suggesting that colonial nesting was not solely a response to nest‐site limitation, but the benefits of breeding colonially (if any) were unclear.
At‐sea behaviour and habitat use by tropicbirds in the eastern Pacific
Authors: SPEAR LARRY B. , AINLEY DAVID G.
Published: March 2005

During the boreal spring and autumn 1980–95, we surveyed Red‐tailed Phaethon rubricauda, White‐tailed P. lepturus and Red‐billed Tropicbirds P. aethereus at sea in the eastern Pacific. Two subpopulations were indicated for both rubricauda and lepturus, based on distribution hiatuses near the South Equatorial Current (see companion paper). Thus, five populations were examined, two each of rubricauda and lepturus, and one of aethereus. During the boreal spring, when equatorial current systems are less well developed, geographical variables (distance from nearest colony and nearest land) were the most important variables affecting tropicbird occurrence. However, sea‐surface salinity and thermal structure of the water column were the primary variables delineating tropicbird occurrence during the boreal autumn. Each tropicbird species utilized different species/sizes of aquatic predators (that make their prey available at the surface) that in turn utilize different oceanographic environments. We suspect that the distribution of aquatic predators is primarily responsible for colony locations and distribution of tropicbird species in the eastern Pacific.
The geopolitics of diaspora
Authors: Carter Sean
Published: March 2005

In recent years there has been a growing body of work dealing with issues of diaspora and hybridity, both within geography and in other disciplines, such as cultural studies. This work tends to celebrate the potential of the hybrid and diasporic to transcend essentialist notions of identity and subjectivity. In this paper I argue that these approaches often fail to pay sufficient attention to two particular aspects of the diaspora experience: firstly, the geographical specificities of particular diasporas, and secondly, the ways in which essentialist modes of being are often reproduced within diasporic discourse. This is done by providing an overview of recent research into the Croatian diaspora in the United States (particularly their involvement in the Balkan conflicts of the 1990s), which begins to develop the notion of the geopolitics of diaspora.
Spaces of change: tribal authorities in the former KaNgwane homeland, South Africa
Authors: King Brian H
Published: March 2005

South Africa's democratic transition has had a significant impact upon localized governance systems in mediating development opportunities within the former apartheid homelands. This paper uses a case study from the former KaNgwane homeland to evaluate the role of the Matsamo Tribal Authority in shaping livelihoods and access to environmental resources. It is argued that although the colonial and apartheid empowerment of the tribal authorities continues to have symbolic and material meaning for rural populations, newly created democratic structures are challenging traditional governance systems in the post‐apartheid era. The intersection between these contrasting, and historically situated, systems suggests a dynamic renegotiation is occurring that will continue to impact rural households within the former places of apartheid.
Efficient use of resources: urban waste ash and soil fertility on the Jos Plateau, Nigeria
Authors: Pasquini M W , Harris F
Published: March 2005

Waste disposal constitutes an acute problem in numerous African cities. One solution could lie in the recycling of the nutrient‐rich waste into agriculture taking place in and around cities. Farmers involved in vegetable production around Jos, Nigeria, have developed a sophisticated soil fertility management strategy combining inorganic fertilizers, manure and urban waste ash. This paper: (1) investigates the socio‐economic constraints linked to obtaining scarce organic inputs, particularly urban waste ash and the health hazards (particularly heavy metal contamination of soil and crops) caused by using this ash and (2) suggests ways to improve use of this important resource.