Background: In birds, the trade-off between the quality and number of nestlings is one of the most important theories of the evolution of life history of birds, which is closely related with climate. We investigated v...Background: In birds, the trade-off between the quality and number of nestlings is one of the most important theories of the evolution of life history of birds, which is closely related with climate. We investigated variation in egg and clutch size of the Black Redstart(Phoenicurus ochruros) on the northeastern edge of the Qinghai-Tibetan Plateau in order to explore and test the relation between egg size and clutch size and the rules governing the variation in these two components with climate change.Methods: We monitored each located nest daily to determine the exact laying order of the eggs and measured their sizes. The variations in egg volume and clutch size between 2008 and 2009 were studied by independent sample t tests. The difference in egg volume in the sequence of the laying order was tested by Kendall's W test and we employed Pearson correlations to investigate the relation between egg size and laying order. All statistical analyses were performed with IBM SPSS Statistics, version 19.0Results: In 2008, the mean egg volume of the Black Redstart was 2.40 and clutch size wer± 0.20 cm^3(n e 2.26 = 50), and the mean clutch size 4.90 ± 0.57(n = 11). In 2009, the mean egg volumeation between eg± 0.18 cm^3(n g size and layin= 74) and 5.20 g order(r ± 0.26(n = 15) respectively. We found a significantly positive correl, while egg size was strongly and negatively correlated with clutch size(r = 0.397, p = 0.030) smaller eggs but a larger clutch in a brood in a resource-rich year, w= h-0.274, p ereas large= 0.002). Black Redstarts tend to layr eggs but smaller clutches are produced in a harsh year.Conclusions: The Black Redstart adopted a "brood survival strategy" to ensure that more offspring could survive. The Black Redstart' trade-off in egg volume and clutch size would guarantee that it will gain maximum benefit in any case.展开更多
The arms race between avian brood parasites and their hosts provides a classic model for studying coevolution.In one of the most widespread obligate brood parasites,the Common Cuckoo(Cuculus canorus),chicks typically ...The arms race between avian brood parasites and their hosts provides a classic model for studying coevolution.In one of the most widespread obligate brood parasites,the Common Cuckoo(Cuculus canorus),chicks typically evict all host progeny(eggs and nestlings)from the nest cup,resulting in complete reproductive failure for the host.Host parents of Common Cuckoos could thus potentially benefit from retrieving evicted eggs and nestlings into the nest cup.However,whether hosts of the Common Cuckoo exhibit such retrieval behavior has been scarcely studied.In this study,we experimentally investigated the occurrence of retrieval in a nestbox-breeding population of Daurian Redstarts(Phoenicurus auroreus),a common cavity-nesting host of the Common Cuckoo.To test the redstarts'response to an egg or a nestling outside the nest cup,we experimentally placed either a conspecific egg,a model cuckoo egg,or a redstart nestling near the rim of the nest cup.We found that redstarts never showed retrieval behavior of either eggs or nestlings.All hosts ignored the experimental nestling and conspecific egg,but most ejected the model cuckoo egg from the nestbox.Our results suggest that selection for retrieval behavior in this cavity-nesting host may be weak or even negative.We discuss several ecological and evolutionary factors that may explain the absence of retrieval in this system.展开更多
基金funded by the National Natural Science Foundation of China (Nos.31301889 and 31070346)the Ph.D. Programs Foundation of the Ministry of Education of China (20120211120040)the Fundamental Research Funds for the Central Universities (lzujbky-2016-89)
文摘Background: In birds, the trade-off between the quality and number of nestlings is one of the most important theories of the evolution of life history of birds, which is closely related with climate. We investigated variation in egg and clutch size of the Black Redstart(Phoenicurus ochruros) on the northeastern edge of the Qinghai-Tibetan Plateau in order to explore and test the relation between egg size and clutch size and the rules governing the variation in these two components with climate change.Methods: We monitored each located nest daily to determine the exact laying order of the eggs and measured their sizes. The variations in egg volume and clutch size between 2008 and 2009 were studied by independent sample t tests. The difference in egg volume in the sequence of the laying order was tested by Kendall's W test and we employed Pearson correlations to investigate the relation between egg size and laying order. All statistical analyses were performed with IBM SPSS Statistics, version 19.0Results: In 2008, the mean egg volume of the Black Redstart was 2.40 and clutch size wer± 0.20 cm^3(n e 2.26 = 50), and the mean clutch size 4.90 ± 0.57(n = 11). In 2009, the mean egg volumeation between eg± 0.18 cm^3(n g size and layin= 74) and 5.20 g order(r ± 0.26(n = 15) respectively. We found a significantly positive correl, while egg size was strongly and negatively correlated with clutch size(r = 0.397, p = 0.030) smaller eggs but a larger clutch in a brood in a resource-rich year, w= h-0.274, p ereas large= 0.002). Black Redstarts tend to layr eggs but smaller clutches are produced in a harsh year.Conclusions: The Black Redstart adopted a "brood survival strategy" to ensure that more offspring could survive. The Black Redstart' trade-off in egg volume and clutch size would guarantee that it will gain maximum benefit in any case.
基金supported by the startup fund from Beijing Normal University(312200502560 to J.Z.)the National Natural Science Foundation of China(32501383 to J.Z.,and 31672297 and 32271559 to W.D.)the Max Planck Society(to B.K.)。
文摘The arms race between avian brood parasites and their hosts provides a classic model for studying coevolution.In one of the most widespread obligate brood parasites,the Common Cuckoo(Cuculus canorus),chicks typically evict all host progeny(eggs and nestlings)from the nest cup,resulting in complete reproductive failure for the host.Host parents of Common Cuckoos could thus potentially benefit from retrieving evicted eggs and nestlings into the nest cup.However,whether hosts of the Common Cuckoo exhibit such retrieval behavior has been scarcely studied.In this study,we experimentally investigated the occurrence of retrieval in a nestbox-breeding population of Daurian Redstarts(Phoenicurus auroreus),a common cavity-nesting host of the Common Cuckoo.To test the redstarts'response to an egg or a nestling outside the nest cup,we experimentally placed either a conspecific egg,a model cuckoo egg,or a redstart nestling near the rim of the nest cup.We found that redstarts never showed retrieval behavior of either eggs or nestlings.All hosts ignored the experimental nestling and conspecific egg,but most ejected the model cuckoo egg from the nestbox.Our results suggest that selection for retrieval behavior in this cavity-nesting host may be weak or even negative.We discuss several ecological and evolutionary factors that may explain the absence of retrieval in this system.
