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Artificial Cuckoo Eggs (artificial + cuckoo_egg)
Selected AbstractsResponses of great reed warblers Acrocephalus arundinaceus to experimental brood parasitism: the effects of a cuckoo Cuculus canorus dummy and egg mimicryJOURNAL OF AVIAN BIOLOGY, Issue 4 2002István Bártol Egg rejection behaviour towards parasitic eggs was studied in a great reed warbler Acrocephalus arundinaceus population in central Hungary, which was heavily (about 65%) parasitised by the common cuckoo Cuculus canorus. Clutches were experimentally parasitised during the egg-laying period with artificial, moderately mimetic cuckoo eggs or with conspecific eggs that were good mimics of the hosts' eggs. Great reed warblers rejected 76.2% of the artificial cuckoo eggs, mainly by ejection, but accepted most of the conspecific eggs (87.5%). Cuckoo eggs in naturally parasitised clutches were rejected at a lower rate (32%). When, in addition to the egg mimicry experiments, a stuffed cuckoo was placed near the nest, accompanied by the recording of a female cuckoo call, hosts' rejection rate of the artificial cuckoo egg increased from 76% to 96%. The sight of the cuckoo, on the other hand, did not influence host's rejection behaviour when a conspecific egg was used in the experiment. A stuffed collared dove Streptopelia decaocto, accompanied by its call, was used as a control, and did not cause any increased rejection. Great reed warblers were more aggressive towards the cuckoo than to the dove dummy. When the cuckoo eggs in naturally parasitised clutches were exchanged with artificial cuckoo eggs, we observed no increase in the rejection rate. We conclude that great reed warblers in our heavily parasitised population are capable of detecting brood parasitism in their clutch by identifying the parasitic egg. The efficiency of this identification depends mainly on the mimicry of the foreign egg. The sight of the cuckoo at the nest may increase rejection rate by stimulus summation, and this conditional effect is mainly affected by the degree of mimicry of the parasitic egg. [source] Experimental Manipulation of Intraclutch Variation in the Great Reed Warbler Shows No Effect on Rejection of Parasitic EggsETHOLOGY, Issue 1 2003Zsolt Karcza In the continuing arms race between hosts and brood parasites, hosts are expected to reduce variation in the appearance of their own eggs within clutches, as it facilitates recognition of parasitic eggs. At the same time, by increasing interclutch variation, hosts should make it more difficult for parasites to evolve perfectly mimetic eggs. In this study, we experimentally manipulated intraclutch variation in the great reed warbler, Acrocephalus arundinaceus, in Hungary, where this species is heavily (c. 64%) parasitized by the common cuckoo, Cuculus canorus. We placed artificial cuckoo eggs, which appeared moderately mimetic to humans, in two groups of nests; in one group we increased variability of egg appearance within clutches by exchanging host eggs among nests. These clutches showed a significantly higher intraclutch variability than natural clutches, which we used as a control group. Our results indicate that it has no effect on rejection behaviour in this species, neither when variation was increased experimentally, nor within the natural range of variation displayed by our population. We suggest that when parasitism is high, selection for reduced intraclutch variation may be less important than frequency-dependent selection for increased variation between individuals within a host population. [source] The common cuckoo Cuculus canorus and its cavity nesting host, the redstart Phoenicurus phoenicurus: a peculiar cuckoo-host system?JOURNAL OF AVIAN BIOLOGY, Issue 4 2002Jarkko Rutila We examined redstart Phoenicurus phoenicurus populations over a period of fifteen years to study interactions between the cuckoo Cuculus canorus and its cavity-nesting host. Over 380 redstart nests were checked and more than 100 cuckoo eggs were found during the study period. The average parasitism rate was 20%. The cuckoos' breeding success was extremely low, only 18 chicks surviving to the fledgling stage. When redstarts were parasitized experimentally with artificial cuckoo eggs, they rejected eight percent of mimetic eggs and 44% of non-mimetic eggs. We were not able to record any rejection of the real cuckoo eggs. However, about 30% of the real cuckoo eggs were found outside the redstart's nest cup. This could be the result of laying failures by the cuckoo, rather than of a strong rejection behaviour by the redstart. We suggest that redstarts' cavity nesting itself was a factor that reduced the cost of the parasitism dramatically. Firstly, it makes it difficult for the female cuckoo to lay her egg correctly in the nest and secondly, it is more difficult for the cuckoo chick to evict the host's eggs or nestlings effectively from the nest. Only 54% of the cuckoo chicks were able to evict all the host eggs or chicks from the nest. When reared in mixed broods, cuckoo chicks survived only in every second case to fledgling age, while at least one redstart chick from every brood managed to leave the nest. [source] Responses of great reed warblers Acrocephalus arundinaceus to experimental brood parasitism: the effects of a cuckoo Cuculus canorus dummy and egg mimicryJOURNAL OF AVIAN BIOLOGY, Issue 4 2002István Bártol Egg rejection behaviour towards parasitic eggs was studied in a great reed warbler Acrocephalus arundinaceus population in central Hungary, which was heavily (about 65%) parasitised by the common cuckoo Cuculus canorus. Clutches were experimentally parasitised during the egg-laying period with artificial, moderately mimetic cuckoo eggs or with conspecific eggs that were good mimics of the hosts' eggs. Great reed warblers rejected 76.2% of the artificial cuckoo eggs, mainly by ejection, but accepted most of the conspecific eggs (87.5%). Cuckoo eggs in naturally parasitised clutches were rejected at a lower rate (32%). When, in addition to the egg mimicry experiments, a stuffed cuckoo was placed near the nest, accompanied by the recording of a female cuckoo call, hosts' rejection rate of the artificial cuckoo egg increased from 76% to 96%. The sight of the cuckoo, on the other hand, did not influence host's rejection behaviour when a conspecific egg was used in the experiment. A stuffed collared dove Streptopelia decaocto, accompanied by its call, was used as a control, and did not cause any increased rejection. Great reed warblers were more aggressive towards the cuckoo than to the dove dummy. When the cuckoo eggs in naturally parasitised clutches were exchanged with artificial cuckoo eggs, we observed no increase in the rejection rate. We conclude that great reed warblers in our heavily parasitised population are capable of detecting brood parasitism in their clutch by identifying the parasitic egg. The efficiency of this identification depends mainly on the mimicry of the foreign egg. The sight of the cuckoo at the nest may increase rejection rate by stimulus summation, and this conditional effect is mainly affected by the degree of mimicry of the parasitic egg. [source] | ||||||||||