Jane Reid

Resource allocation between reproductive phases: the importance of thermal conditions in determining the cost of incubation

Changes in the resources allocated to particular stages of reproduction are expected to influence allocation to, and performance in, subsequent reproductive stages. Experimental manipulation of individual investment patterns provides important evidence that such physiological trade‐offs occur, and can highlight the key environmental variables that influence reproductive costs. By temporarily altering the thermal properties of starling nests, we reduced the energetic demand of first‐clutch incubation, and examined the effect of this manipulation on performance during the same and the subsequent reproductive attempts. Compared with controls, starlings investing less in incubation were more successful in fledging young, and were more likely to hatch all their eggs if a subsequent reproductive attempt was made. Our results show that incubation demands can limit reproductive success, and that resources saved during incubation can be reallocated to later stages of the same reproductive attempt and to future reproductive attempts. This study also shows that small changes in thermal environment can affect breeding success by altering the energetic demands imposed on incubating parents, independently of the effect of temperature on other environmental variables such as food supply.

USING ARTIFICIAL NESTS TO TEST IMPORTANCE OF NESTING MATERIAL AND NEST SHELTER FOR INCUBATION ENERGETICS

Abstract Incubation is an energetically demanding process for parents, in part because of the thermodynamic costs of maintaining egg temperature. One might predict that aspects of nest construction—in particular, the thermodynamic properties of the nesting material and the degree to which the nest provides shelter from the wind—would have important effects on thermodynamic costs. However, little is known about the relative importance of those factors. Here, we investigate egg cooling rates in several commonly used nesting materials and in various wind speeds and examine the effect on those rates of wetting the materials. Nesting materials differ greatly in their insulating properties; feather down is the best insulator, and grass the worst. When the materials are wet, eggs cool much more rapidly, differences between materials tend to diminish, and down becomes the worst insulator. Hence, there may be significant selection pressure to choose particular nesting materials, but materials may be better or worse according to the situation of the nest. Increasing wind speed also has profound effects on egg cooling rates, even at the low speeds tested here, which implies strong selection pressure to locate and construct nests that minimize wind speed at the egg surface. Our results suggest that nest construction may have an important bearing on the subsequent costs of reproduction, and that important trade-offs may exist between nest construction for reduced thermodynamic costs, and other costs and benefits of nest-building and reproduction.

A Task-Oriented Non-Interactive Evaluation Methodologyfor Information Retrieval Systems

Past research has identified many different types of relevance in information retrieval (IR). So far, however, most evaluation of IR systems has been through batch experiments conducted with test collections containing only expert, topical relevance judgements. Recently, there has been some movement away from this traditional approach towards interactive, more user-centred methods of evaluation. However, these are expensive for evaluators in terms both of time and of resources. This paper describes a new evaluation methodology, using a task-oriented test collection, which combines the advantages of traditional non-interactive testing with a more user-centred emphasis. The main features of a task-oriented test collection are the adoption of the task, rather than the query, as the primary unit of evaluation and the naturalistic character of the relevance judgements.

ENERGETIC CONSEQUENCES OF CLUTCH TEMPERATURE AND CLUTCH SIZE FOR A UNIPARENTAL INTERMITTENT INCUBATOR: THE STARLING

Abstract In uniparental intermittent incubators, incubating parents must simultaneously regulate both the temperature of the clutch and their own energy level. To examine energetic consequences of providing different thermal environments for clutches of different sizes, a dynamic model was constructed in which energy level of an incubating European Starling (Sturnus vulgaris) and temperature of its clutch were simultaneously described. Adult energy balance after a day of incubation decreased as mean clutch temperature increased, such that the debt accrued while maintaining a clutch within the optimal developmental temperature range (36–39°C) was predicted to be prohibitively high, despite the prediction that the mean basal metabolic rate (BMR) required to maintain this temperature was <2 BMR. Thus, this model can explain our observation that starlings maintained their eggs at 32–33°C, well below the developmental optimum. Consistent with empirical studies, our model predicted that the metabolic demand of incubation increases with clutch size. That increase was predicted to affect adult energy balance and hence cost of incubation when starlings maintained their clutches at optimal temperatures, but not at the lower temperatures actually observed. Hence, clutch-size-dependent variation in incubation demands may be unlikely to influence optimal number of eggs that a starling should lay. However, exact relationship between clutch size and adult energy debt depended on the nature of the relationship between clutch size and clutch thermal properties and on mean incubation temperature. Thus, consequences of clutch size for the cost of incubation are not clearly predictable, and caution may be required when using experimental clutch enlargements to manipulate reproductive costs.

Construction of a test collection for the focussed retrieval of structured documents

In this paper, we examine the methodological issues involved in constructing test collections of structured documents and obtaining best entry points for the evaluation of the focussed retrieval of document components. We describe a pilot test of the proposed test collection construction methodology performed on a document collection of Shakespeare plays. In our analysis, we examine the effect of query complexity and type on overall query difficulty, the use of multiple relevance judges for each query, the problem of obtaining exhaustive relevance assessments from participants, and the method of eliciting relevance assessments and best entry points. Our findings indicate that the methodology is indeed feasible in this small-scale context, and merits further investigation.

POSTFLEDGING SURVIVAL, MOVEMENTS, AND DISPERSAL OF RING OUZELS (TURDUS TORQUATUS)

ABSTRACT. Recent evidence suggests that avian population growth rates may be constrained by low postfledging survival. Therefore, quantifying postfledging mortality and understanding the ecological factors that influence it are fundamental for assessing the relative importance of this life-history stage for population growth and identifying the ecological drivers of population dynamics. We radiotracked 110 juvenile Ring Ouzels (Turdus torquatus), a species of high conservation concern in the United Kingdom, to test hypotheses regarding the timing and causes of postfledging mortality and to quantify the timing and magnitude of local movements and dispersal. Juveniles fledged from early-season broods had higher survival during each 4-day period over 116 days postfledging (0.952 ± 0.011 [SE]) than juveniles fledged from late-season broods (0.837 ± 0.021). Most mortality occurred within the first 3 weeks postfledging, and predation by raptors and mammals was the main apparent cause of mortality, accounting for 59% and 27% of deaths, respectively. Juvenile survival decreased at the age of independence from parental care. Juveniles traveled increasing distances from their nests with time after fledging, and those that fledged early in the season dispersed outside the study area at significantly older ages than those that fledged late in the season.

Automatic identification of best entry points for focused structured document retrieval

Focussed structured document retrieval employs the concept of best entry points (BEPs), which are intended to provide optimal starting-points from which users can browse to relevant document components. This paper describes two small-scale studies, using experimental data from the Shakespeare user study, which developed and evaluated different approaches to the problem of automatic identification of BEPs.

Evaluation of a Prototype Interface for Structured Document Retrieval

Document collections often display either internal structure, in the form of the logical arrangement of document components, or external structure, in the form of links between documents. Structured document retrieval systems aim to exploit this structural information to provide users with more effective access to structured documents. To do this, the associated interface must both represent this information explicitly and support users in their browsing behaviour. This paper describes the implementation and user-centred evaluation of a prototype interface, the RelevanceLinkBar interface. The results of the evaluation show that the RelevanceLinkBar interface supported users in their browsing behaviour, allowing them to find more relevant documents, and was strongly preferred over a standard results interface.