2,941 research outputs found
Effect of timing and female quality on clutch size in the Collared Flycatcher Ficedula albicollis
Capsule: Laying date and female age appear to be related to clutch size.
Aims: To test two hypotheses ('date' and 'quality'), which might explain why fewer eggs are laid late in the season.
Methods: Four years of data and multivariate analysis were used to test the effects of timing of breeding and female quality reflected by morphological variables and age on clutch size in the Collared Flycatcher Ficedula albicollis. We estimated food supply during parental care by measuring diet composition of nestlings.
Results: We distinguished the independent effects of date and age of females on clutch size. The type of prey fed to nestlings was different early and late in the season. Hence food supply during the nestling care period may be a limiting environmental factor that indirectly determines clutch size.
Conclusion: Our results are consistent with the predictions of the date hypothesis, but the quality hypothesis was also partially supported. Depending on year effects, 30-50% of the variance in clutch size may be related to the timing of breeding and an additional 5-10% may be due to quality (age) differences between early- and late-breeding birds
Multi-Agent Cooperation for Particle Accelerator Control
We present practical investigations in a real industrial controls environment
for justifying theoretical DAI (Distributed Artificial Intelligence) results,
and we discuss theoretical aspects of practical investigations for
accelerator control and operation. A generalized hypothesis is introduced,
based on a unified view of control, monitoring, diagnosis, maintenance and
repair tasks leading to a general method of cooperation for expert systems
by exchanging hypotheses. This has been tested for task and result sharing
cooperation scenarios. Generalized hypotheses also allow us to treat the
repetitive diagnosis-recovery cycle as task sharing cooperation. Problems
with such a loop or even recursive calls between the different agents are
discussed
Beliefs and Conflicts in a Real World Multiagent System
In a real world multiagent system, where the
agents are faced with partial, incomplete and
intrinsically dynamic knowledge, conflicts are
inevitable. Frequently, different agents have
goals or beliefs that cannot hold simultaneously.
Conflict resolution methodologies have to be
adopted to overcome such undesirable occurrences.
In this paper we investigate the application of
distributed belief revision techniques as the support
for conflict resolution in the analysis of the
validity of the candidate beams to be produced
in the CERN particle accelerators.
This CERN multiagent system contains a higher
hierarchy agent, the Specialist agent, which
makes use of meta-knowledge (on how the conflicting
beliefs have been produced by the other
agents) in order to detect which beliefs should be
abandoned. Upon solving a conflict, the Specialist
instructs the involved agents to revise their
beliefs accordingly.
Conflicts in the problem domain are mapped into
conflicting beliefs of the distributed belief revision
system, where they can be handled by
proven formal methods. This technique builds
on well established concepts and combines them
in a new way to solve important problems. We
find this approach generally applicable in several
domains
Depigmented wing patch size is a condition-dependent indicator of viability in male collared flycatchers
Honesty of sexual advertisement is thought to be the result of signalling costs. Because production costs of depigmented plumage patches are probably very low, their role as honest signals of individual quality has been questioned. Costs of bearing these traits, however, should also be taken into account. Studies on proximate determination and possible information content of white badges are very rare. We investigated repeatability, sensu lato heritability, and condition- and age-dependence of white wing patch size, a male display trait in a population of collared flycatchers (Ficedula albicollis), based on 4 years of data. By comparing relationships between age and wing patch size (1) within individuals among years versus (2) among individuals within years, we could address the viability indicator value of the trait. Wing patch size approximately doubled at the transition from subadult to adult plumage, and its change was significantly related to body condition the previous season. Repeatability and heritability values suggest that the trait is informative already in subadult plumage, and that genetic and early environmental effects are important in its determination, the latter only during the first year of life. Thus, wing patch size can act as a condition-dependent signal of genetic quality. Indeed, discrepancy between results from the horizontal and vertical age-dependence approaches shows that the trait was positively related to expected lifespan. After examining several alternative explanations, we conclude that wing patch size indicates genetically based viability. This is the first study to demonstrate a good genes viability benefit conferred by a depigmented plumage patch
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