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Abstract

As there is geographic and temporal variation in the rate at which reed warblers Acrocephalus scirpaceus are parasitised by the cuckoo Cuculus canorus , phenotypic plasticity of defences against parasitism could be advantageous. Three experiments were conducted using three populations of reed warblers, parasitised by cuckoos to varying degrees, to test if reed warbler defences against parasitism are plastic. In an unparasitised and a rarely parasitised population, attempts to simulate the presence of cuckoos at the nest or in the habitat failed to stimulate an increase in rates of egg rejection. However, three lines of evidence supported the view that both unparasitised and parasitised populations were similarly able to discriminate odd eggs but that there is phenotypic plasticity in the decision to reject those eggs. First, reed warblers at all populations pecked model eggs, thereby indicating recognition of the model egg as a foreign egg, but varied in their tendency to reject them. Second, reed warblers at two populations, one unparasitised and the other frequently parasitised, rejected brown painted reed warbler eggs at the same rate, suggesting that there are no differences between populations in the ability to reject some types of eggs. Finally, rates of rejection decreased seasonally only at the frequently parasitised population. These results suggest that phenotypic plasticity can explain population differences in rates of egg rejection, but do not rule out the possibility that genetic differences also contribute to differences between populations.

In: Behaviour

Abstract

Two potential defences against brood parasitism by the cuckoo Cuculus canorus were compared experimentally between British populations of reed warblers Acrocephalus scirpaceus that are parasitised at different rates. (1) Rates of rejection of model cuckoo eggs were lower at two unparasitised populations which did not have resident cuckoos, than at a rarely parasitised population which had cuckoos nearby, and at a regularly parasitised population. (2) Reed warblers from an unparasitised population showed a slightly weaker response to taxidermic mounts of cuckoos and, unlike a parasitised population, did not differentiate between mounts of a cuckoo, sparrowhawk Accipiter nisus and jay Garrulus glandarius . Differences in exposure to real predators may explain the differences in responses to mounted predators between populations, as specific aggressive responses to predators are likely to have been learned. Although evidence from dispersal and population turnover data suggests that there is likely to be gene flow between reed warbler populations in Britain, the hypothesis that the population differences reflect genotypic differences could not be ruled out. An alternative explanation of phenotypic plasticity in defences could also explain the population differences. Phenotypic plasticity in defences would be favoured in environments where the risk of parasitism fluctuates, if those defences are costly to unparasitised reed warblers.

In: Behaviour
Christoph Schlingensief lebt, die Avantgarde lebt. Beide totzusagen, wäre ein Abgesang auf die transformative Kraft der Kunst. Christoph Schlingensief setzte sich in seiner Arbeit über mehr als vier hochproduktive Jahrzehnte mit avantgardistischen Bewegungen der Musik, der darstellenden und bildenden Künste, der Literatur und des Films auseinander. Seine heterogenen Verweise stellen die Vielfalt dessen aus, was zwischen der performativen Lautmalerei des Dadaismus und dem erweiterten Kunstbegriff von Joseph Beuys als Avantgarde gilt. In den Analysen, Theoriediskussionen und Erinnerungen dieses Bandes, die sich den prominentesten Bezugnahmen in Schlingensiefs Filmen, Inszenierungen, Aktionen und Installationen auf avantgardistische Stilrichtungen und Programme widmen, wird somit auch deutlich, wie Schlingensief selbst avantgardistisch wirksam wurde, und die Kunstwelt in ihrem Selbstverständnis transformierte und belebte.