Why do Gull-billed Terns Gelochelidon nilotica feed on fiddler crabs Uca tangeri in Guinea-Bissau?

Gull-billed Terns Gelochelidon nilotica wintering in Guinea Bissau mainly fed on fiddler crabs Uca tangeri and were occasionally seen feeding on fish and locusts. As fiddler crabs have a low energy content, terns need a large gross intake to meet daily energy demands. Fiddler crabs also have a low ratio of digestible flesh to exoskeleton, and therefore tern food intake may be limited by gut capacity. Activity budgets of Gullbilled Terns feeding on fiddler crabs showed that a considerable part of the time was spent resting. The duration of resting intervals increased with energy intake and was positively correlated with the metabolisable energy content of the crab eaten, suggesting that resting periods were required for a proper digestion. The poor quality of fiddler crabs was offset by high capture rates. So daily energy expenditure of the terns could easily be met by feeding on fiddler crabs. Even when resting pauses were included in foraging time, foraging for only 1.5 hours on fiddler crabs satisfied the terns&rsquo; daily energy demands. Instead, feeding on energy-rich fish would require about 2.5 hours to satisfy daily energy demands. Compared to the more specialised piscivorous Little Tern Sternula albifrons and Sandwich Tern Sterna sandvicensis, capture rate of fish was poor in Gull-billed Terns. From an energetic point of view, wintering Gull-billed Terns feeding on fiddler crabs seem to have an easy living in Guinea Bissau.<br /

Conversion disorder and/or functional neurological disorder:How neurological explanations affect ideas of self, agency, and accountability

An estimated 15% of patients seen by neurologists have neurological symptoms, such as paralysis, tremors, dystonia, or seizures, that cannot be medically explained. For a long time, such patients were diagnosed as having conversion disorder (CD) and referred to psychiatrists, but for the last two decades or so, neurologists have started to pay more serious attention to this patient group. Instead of maintaining the commonly used label of conversion disorder – which refers to Freud’s idea that traumatic events can be converted into deviant behaviour – these neurologists use the term functional neurological disorder (FND) and explain that the problems are due to abnormal central nervous system functioning. The situation that some patients with medically unexplained neurological symptoms are diagnosed with CD and treated by psychiatrists while others are diagnosed with FND and stay under the control of neurologists provides a unique case for analysing how neurological and psychological explanations affect subjectivity. In this article, I compare patient reports from English-language websites from the past 15 years to find out how minds, bodies, brains, and selves act and interact in the accounts of both patient groups. I conclude that the change in label from CD to FND has not only influenced ideas of medically unexplained disorders, but also affected ideas of the self and the body; of self-control and accountability

Brain technologies of the self:how working on the self by working on the brain constitutes a new way of being oneself

Zorg dragen voor jezelf wordt steeds vaker geïnterpreteerd als zorg dragen voor je brein. Naast pillen, boeken, voedingsmiddelen en games voor een ‘beter brein’, zijn er ook diverse apparaten op de markt waarmee mensen hun eigen hersenen kunnen stimuleren. Deze apparaten, werkend met licht en geluid, elektrische of magnetische stimulatie, of met feedback op de hersengolfactiviteit, worden aangeboden voor klachten variërend van stress, burn-out, angst, depressie, of ADHD tot het verbeteren van de cognitieve of creatieve vermogens. Dit proefschrift beschrijft de historische achtergrond en het eigentijdse gebruik van deze apparaten. Ik analyseer de wijze waarop de effecten van deze apparaten werden en worden gedemonstreerd; hoe gebruikers van neurofeedback (hersengolftraining) een nieuwe vorm van zijn creëren waarbij het zelf wordt uitgebreid met de hersenen en allerlei andere psychologische, fysiologische, materiële of spirituele entiteiten; hoe de cliënt, de behandelaar en andere actoren (computer, hersenkaart, hersengolven) moeten samenwerken om de neurofeedback succesvol te laten verlopen; en hoe de persoonlijke overtuigingen, ideeën en frustraties van (vroegere) hersengolfwetenschappers ten aanzien van het zelf en het brein hebben bijgedragen aan deze eigentijdse manier van zijn. In andere woorden, dit proefschrift is een historische, etnografische en theoretische zoektocht naar de wijze van zelf die wordt geconstitueerd als mensen zichzelf proberen te verbeteren met een hersenapparaat

Pilot study on the influence of feeding conditions at the North Sea on the breeding results of the Sandwich Tern <i>Sterna sandvicensis</i>

Of all gulls and terns breeding along the Dutch coast the Sandwich Tern is the most specialised piscivorous bird. During the breeding season terns feed mainly on pelagic fish as herring, sprat, sandeel, and lesser sandeel. This makes the species extremely vulnerable to changes in the marine ecosystem.During the twentieth century, the number of breeding Sandwich Terns in the Netherlands has shown large fluctuations. In the beginning of this century, numbers were low, because of large-scale egg-collecting and shooting of adults. As a result of the protection following the slaughter for the lady's hat fashion, numbers gradually increased up to 45,000 pairs in 1938. In World War II, egging again caused a drop in numbers. After World War 11, the population increased up to 36,000 pairs in the 1950s. At the end of that decade, numbers dropped markedly and the number of breeding pairs were reduced to 875 in 1965. This decrease was due to a pollution of the Dutch coastal waters by organochlorine pesticides. After the pollution stopped, the population increased in numbers again, but the large numbers from the period previous to the pollution have never been reached since then. Compared to previous population recoveries, the recovery after the pollution in the 1960s was slow, and since the 1 980s the population seems to stabilise at approximately 11,000 breeding pairs, almost one third of the population during the 1930s and the 1950s.This leads to the main subject of this report: 'What is the reason of the slow recovery of the Sandwich Tern after the numerical decline in the 1960s and why is there a stabilisation of breeding pairs at such a low level?’. Although this could be due to many factors, we have focussed our study on the food situation during the chick rearing period, The study deals with three items:( 1 ) What is the species composition and what is the length distribution of prey items delivered to the chicks of Sandwich Terns on Griend, the main colony in The Netherlands, and have there been remarkable shifts compared with the late 1960s and early 1970s (chapter 2)?(2) Where do the terns feed, and are there any shifts in this respect compared with the late 1 960s and early 1970s (chapter 3)?(3) Is there a relationship between fish availability and either population size or breeding success of the Sandwich Tern (chapter 4)?The species composition of the fish delivered to the chicks in 1992-1993 was identical to that in 1969-1974. The number of fish brougth to the chicks, however differed markedly from that in 1969-1974. In bath years (mast pronounced in 1992) the food supply was law compared with 1969-1974, and also compared with foreign colonies. The amount of food actually eaten by the chicks was strongly influenced by windspeed. An increasing windspeed did not only lower the supply of food (resulting from a lower foraging success) but also increased kleptoparasitism by Black- headed Gulls. The low food supply in recent times might be a possible explanation for the stabilisation of the number of breeding pairs since the early 19805.Experiments with radio-tagged adults revealed that the foraging area of the terns is not markedly different from that in 1970, although there a little shift towards the Wadden Sea.Analyses of data on the abundance of young herring in the North Sea and the number of breeding Sandwich Terns revealed a positive relationship between these two parameters. However, the number of fledged young showed no relationship with the abundance of young herring. Although the data set on young herring refers to the total North Sea and do not necessarily show the local abundance of this species, the results suggest that the breeding population of the Sandwich Tern at Griend is regulated by the availability of food