A comparative study of host selection in the European cuckoo Cuculus canorus (original) (raw)
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The Auk, 2009
Resumen.-Existe abundante evidencia de que los individuos dentro y entre poblaciones hospederas no son parasitados de manera uniforme por Cuculus canorus. Primero, investigamos si el canto y el tamaño del nido de una especie hospedera, Acrocephalus arundinaceus, otorga información sobre las habilidades parentales y el nivel de defensa en contra de C. canorus. Segundo, analizamos si la preferencia de las hembras de C. canorus por los nidos hospederos es predicha por el grado de expresión del canto y el tamaño del nido del hospedero. Los hospederos que criaron más temprano construyeron nidos más grandes, fueron cantantes más activos y presentaron repertorios menos ricos en sílabas que los individuos que criaron más tarde. Los pichones de los hospederos criados en nidos grandes recibieron más alimento que aquellos criados en nidos pequeños. Los machos hospederos que fueron cantantes activos se aparearon con las hembras que construyeron nidos más grandes. Todas las parejas de hospederos rechazaron los huevos artificiales no miméticos, pero aquellas con nidos grandes fueron más propensas a rechazar los huevos naturales de C. canorus. Así, las parejas de A. arundinaceus con nidos grandes estuvieron más dispuestas a alimentar a los pichones de C. canorus, pero también presentaron mayores habilidades para discriminar sus huevos, que aquellas parejas con nidos pequeños. Estos resultados, y la incapacidad de la hembra de C. canorus de captar la información suministrada por las señales sexuales de A. arundinaceus, pueden explicar por qué las hembras siguieron una regla simple de seleccionar los nidos hospederos más visibles de la población.
Evolutionary Ecology, 2009
We investigated the hypothesis that the common cuckoo Cuculus canorus selects host pairs of good phenotypic quality. As there is some evidence that cuckoos may select hosts within a population non-randomly based on external cues reflecting their foster abilities, we predicted that great reed warbler Acrocephalus arundinaceus pairs parasitized by the cuckoo would exhibit higher quality than unparasitized ones. To test this assumption, we evaluated two different parameters indicating host quality: body condition and characteristics of host eggs. We found that parasitized females showed significantly better body condition than unparasitized ones, and the model showed that the probability of being parasitized by the cuckoos increased with increasing body condition. Moreover, the likelihood of being parasitized by a cuckoo within the great reed warbler population increased with decreasing colour variability within clutches: parasitized females allocated costly blue pigments to eggshells more equally compared with unparasitized ones. Our study revealed that cuckoos parasitize great reed warbler females of higher quality, as reflected in host body condition and egg colour characteristics. In highly mimetic systems, cuckoos may choose to parasitize hosts with eggs displaying low intraclutch variation, both because this leads to reduced rejection and because these hosts are of high quality.
Common Cuckoo Cuculus canorus and host behaviour at Reed Warbler Acrocephalus scirpaceus nests
Ibis, 2008
This study is based on continuous video recordings made at 53 Reed Warbler Acrocephalus scirpaceus nests each day during the laying period. Egg-laying by the Common Cuckoo Cuculus canorus was recorded in 14 (26.4%) of these nests. By analysing the activity of the host birds around and at the nest, we found that this is probably not the only cue used by the Common Cuckoo when locating suitable nests to parasitize. Furthermore, in most cases there was no significant difference between the length of time the host birds spent a t the nest in the morning and afternoon, thus providing little support for the hypothesis that the Common Cuckoo lays in the afternoon because it is less likely to be seen by the nest owners then. Parasitized Reed Warblers rejected the Common Cuckoo egg more frequently when they observed the parasite at their nests. However, contrary to what should be expected, most Common Cuckoos laid their eggs in the presence of the host(s), and in general their egg-laying behaviour (for cxamplc duration of stay at the nest) was less secretive than described earlier. When partially depredating host clutches, Cuckoos showed the same behavioural pattern at parasitized and unparasitized nests, indicating that the latter may act as a potential reserve for egg-laying.
The evolution of egg rejection by cuckoo hosts in Australia and Europe
Behavioral Ecology, 2005
Exploitation of hosts by brood parasitic cuckoos is expected to stimulate a coevolutionary arms race of adaptations and counteradaptations. However, some hosts have not evolved defenses against parasitism. One hypothesis to explain a lack of host defenses is that the life-history strategies of some hosts reduce the cost of parasitism to the extent that accepting parasitic eggs in the nest is evolutionarily stable. Under this hypothesis, it pays hosts to accept cuckoo eggs if (1) the energetic cost of raising the cuckoo is low, (2) there is time to renest, and clutch size is small. We parasitized the nests of host and nonhost species with nonmimetic model eggs to test whether the evolution of egg recognition by cuckoo hosts could be explained by life-history variables of the host. The most significant factor explaining rates of rejection of model eggs was whether or not a species was a cuckoo host, with hosts rejecting model eggs at a higher rate than nonhosts. Egg-rejection rates were also explained by visibility within the nest and by cuckoo mass. We found little support for the life-history model of egg rejection. Our results suggest that parasitism is always sufficiently costly to select for host defenses and that the evolution of defenses may be limited by proximate constraints such as visibility within the nest.
Reviewing 30 years of studies on the Common Cuckoo: accumulated knowledge and future perspectives
Chinese Birds, 2013
In Europe, eggs of the Common Cuckoo (Cuculus canorus) have been found in more than 125 different host species. However, very few species are frequently parasitized. The Cuckoo is divided into several distinct races termed gentes. Females of each gens specialize in parasitizing a particular host species. More than 20 such gentes are recognized in Europe. Each female Cuckoo lays eggs of constant appearance. Most gentes can be separated based on their distinct egg types, which in many cases mimic those of their hosts. Different gentes may occur in sympatry or may be separated geographically. Some gentes may occur in restricted parts of the host's distribution area. These patterns raise some fundamental questions like: Why are some passerine species preferred as hosts while others are not? Why does a host population consist of individuals either accepting or rejecting Cuckoo eggs? Why is there marked variation in egg rejection behavior between various host populations? How distinct and host-specialized are Cuckoo gentes? These questions are discussed in relation to existing knowledge and future perspectives.
Breeding site and host selection by Horsfield's bronze-cuckoos, Chalcites basalis
Animal Behaviour, 2007
Cuckoos are faced with a series of reproductive decisions unique to the brood-parasitic lifestyle. Choice of the appropriate host to rear their young requires decision making at three levels. First, selection of a breeding site may take into account host densities in addition to environmental considerations. Second, once they have selected a breeding site, female cuckoos must ensure that they choose the nests of an appropriate host species to rear their young. Third, cuckoos may also choose among individuals of the host species in relation to the likelihood that the host will successfully rear their young. By observation and experiment, we investigated the factors that influenced annual parasitism rates and the mechanisms of host choice in Horsfield's bronze-cuckoos, Chalcites basalis. Parasitism rates varied from 0% to 37% annually, and were influenced by host density and spring rainfall. Despite the availability of several suitable hosts with similar nest sites within the same habitat, over 99% of Horsfield's bronze-cuckoo eggs were laid in superb fairywren, Malurus cyaneus, nests, lending strong support to the Host Preference Hypothesis for host choice. Patterns of parasitism were nonrandom with respect to host female age and identity, but we found no evidence that cuckoos preferentially parasitized those individuals that were most likely to successfully rear their young.
Ibis, 2002
An unusually high frequency (64%) of European Cuckoo Cuculus canorus parasitism was found in Great Reed Warbler Acrocephalus arundinaceus clutches in central Hungary. Sixtyfour per cent of the parasitized clutches contained one Cuckoo egg, 23% contained two, 10% had three and 3% had four. This means that 58% of the Cuckoo eggs were found in multiply parasitized clutches. In multiple parasitism the laying second Cuckoo removed an egg from the clutch randomly, so preferred neither the host eggs, nor the concurrent Cuckoo egg. Host response towards the parasitic eggs showed 66% acceptance, 12% ejection, 20% desertion and 2% egg burial. We found great variation in both the host and the parasitic egg colour and pattern. This reduces the chance that the parasitic egg's appearance matched that of the hosts' but, in spite of this, almost perfect mimesis was found in 28% of the Cuckoo eggs. Poorly mimetic Cuckoo eggs were more frequently rejected by Great Reed Warblers than parasite eggs that were very similar to the host eggs. This high level of mimicry sometimes makes it difficult for the observer to identify the parasitic egg, especially when it is similar in size to the host eggs. It is also difficult for the host, as shown by the relatively high recognition error and ejection cost.
Behavioral Ecology and Sociobiology, 2010
Hosts of the common cuckoo (Cuculus canorus), an avian brood parasite, develop antiparasite defense mechanisms to increase their reproductive success. Ejection of the parasite egg and desertion of the parasitized nest are the most typical adaptations in response to brood parasitism, but nest desertion may also occur in response to partial clutch reduction, independently from parasitism. Some great reed warblers (Acrocephalus arundinaceus) showed both mechanisms in the same incidence of cuckoo parasitism: in 18% of successful ejections of the parasite eggs, they deserted their nests. We studied if such cases of post-ejection nest-desertion are caused by brood parasitism or reduced clutch value. We experimentally parasitized clutches consisting of five or three host eggs with two painted conspecific eggs to mimic parasitic eggs, as multiple parasitism is frequent in the area. Although hosts ejected these parasitic eggs in both clutch categories (100% and 67% for the larger and smaller inital clutch sizes, respectively), we found that after manipulation, postejection nest-desertion frequently occurred at small (3-egg) clutches (40%), but rarely at large (5-egg) clutches (17%). The same phenomenon also occurred when unparasitized 3-egg clutches were reduced by two eggs, but not when 5-egg clutches were reduced in the same way. A logistic regression model revealed that only initial clutch size affected nest desertion of parasitized nests in our experiments. Therefore, we conclude that post-ejection nest-desertion is not a second antiparasite mechanism, which might serve as a redundant antiparasite defense, but a reaction to typically small and further decreased clutch size. Keywords Cuckoo. Great reed warbler. Antiparasite defense. Clutch size. Clutch reduction The common cuckoo (Cuculus canorus, hereafter "cuckoo") is a well-known brood parasite, which parasitizes more than a hundred small passerine species breeding in the Palearctic (Wyllie 1981; Davies 2000; Payne 2005). However, the number of regularly used hosts is much smaller, probably just over 20, and at least 17 host-specific races of the cuckoo (the so-called "gentes") with developed egg mimicry were previously found in Europe (Moksnes and Røskaft 1995; Alvarez 1994; Antonov et al. 2007), with additional species in Asia (Higuchi 1998; Lee and Yoo 2004; Takasu et al. 2009). The coevolutionary processes between cuckoos and their avian hosts are typically explained as a coevolutionary arms race (Dawkins and Communicated by M. Soler