Background:Red-winged Blackbirds(Agelaius phoeniceus),hereafter red-wings,are much less frequently parasitized by Brown-headed Cowbirds(Molothrus ater)in eastern North America than in central North America and had not...Background:Red-winged Blackbirds(Agelaius phoeniceus),hereafter red-wings,are much less frequently parasitized by Brown-headed Cowbirds(Molothrus ater)in eastern North America than in central North America and had not been recorded as hosts in our study area in southeastern Pennsylvania.Although hosts of Old World cuckoos(Cuculidae)often show geographic variation in egg rejection behavior,cowbird hosts typically exhibit uniform responses of all acceptance or all rejection of cowbird eggs.Thus,geographic variation in cowbird parasitism frequencies might reflect a different behavioral response to parasitism by hosts where only some populations reject parasitism.In this study,we tested whether egg rejection behavior may explain the lack of parasitism observed in our eastern red-wing population,which may provide insight into low parasitism levels across eastern North America.Methods:We parasitized red-wing nests with model cowbird eggs to determine their response to parasitism.Nests were tested across three nest stages and compared to control nests with no manipulations.Because rejection differed significantly by stage,we compared responses separately for each nest stage.We also monitored other songbird nests to identify parasitism frequencies on all potential hosts.Results:Red-wings showed significantly more rejections during the building stage,but not for the laying and incubation stages.Rejections during nest building involved mostly egg burials,which likely represent a continuation of the nest building process rather than true rejection of the cowbird egg.Excluding these responses,red-wings rejected 15%of cowbird eggs,which is similar to rejection levels from other studies and populations.The overall parasitism frequency on 11 species surveyed in our study area was only 7.4%.Conclusions:Egg rejection behavior does not explain the lack of parasitism on red-wings in our eastern population.Alternatively,we suggest that cowbird preference for other hosts and the low abundance of cowbirds in the east might explain the lack of parasitism.Future research should also explore cowbird and host density and the makeup of the host community to explain the low levels of parasitism on red-wings across eastern North America because egg rejection alone is unlikely to explain this broad geographic trend.展开更多
Wallace Stevens is one of five greatest poets in America in 20th century. The relation between imagination and reality is a major theme of his poems. He holds the view that the mission of poets is to build a bridge li...Wallace Stevens is one of five greatest poets in America in 20th century. The relation between imagination and reality is a major theme of his poems. He holds the view that the mission of poets is to build a bridge linking the world of imagination and of reality with the result of deconstructing the logic of binary opposition since the time of Plato. Thirteen Ways of Looking at A Blackbird is a representative poem that expresses Wallace’s thoughts of deconstruction. This article is to probe into how the poet establishes the reality dominated by imagination and then how he deconstructs the binary opposition between imagination and reality since the time of Plato.展开更多
This paper reports breeding ecology of Blackbird(Turdus merula mandarinus) in Feixi County,Anhui Province from March to July of 1996.The bird nested in resident quarters earlier than in forests.In the case of breeding...This paper reports breeding ecology of Blackbird(Turdus merula mandarinus) in Feixi County,Anhui Province from March to July of 1996.The bird nested in resident quarters earlier than in forests.In the case of breeding in forests,they neted on the trees at the edge of forests near pond.They were compatible with large birds such as heons.The parent-birds attacked violently anyone who contacted their young birds.There were only a few nestlings growing up to leave their nests.Survval rate was determined mainly by weather.The equation of the growth of body weight was W=77 3/[1+e -0 472(t-6 4) ].Compared with the other passerines,such as Blue-winged Pitta and Red-rumped Swallow,nestlings of Blackbird grew up rapidly,leaving their nest with lighter body mass.For the first time,Cuckoo was found laying egg in the nest of Blackbird in China.展开更多
基金provided by a BEARS Grant and a Neag Undergraduate Research Grant from Kutztown University
文摘Background:Red-winged Blackbirds(Agelaius phoeniceus),hereafter red-wings,are much less frequently parasitized by Brown-headed Cowbirds(Molothrus ater)in eastern North America than in central North America and had not been recorded as hosts in our study area in southeastern Pennsylvania.Although hosts of Old World cuckoos(Cuculidae)often show geographic variation in egg rejection behavior,cowbird hosts typically exhibit uniform responses of all acceptance or all rejection of cowbird eggs.Thus,geographic variation in cowbird parasitism frequencies might reflect a different behavioral response to parasitism by hosts where only some populations reject parasitism.In this study,we tested whether egg rejection behavior may explain the lack of parasitism observed in our eastern red-wing population,which may provide insight into low parasitism levels across eastern North America.Methods:We parasitized red-wing nests with model cowbird eggs to determine their response to parasitism.Nests were tested across three nest stages and compared to control nests with no manipulations.Because rejection differed significantly by stage,we compared responses separately for each nest stage.We also monitored other songbird nests to identify parasitism frequencies on all potential hosts.Results:Red-wings showed significantly more rejections during the building stage,but not for the laying and incubation stages.Rejections during nest building involved mostly egg burials,which likely represent a continuation of the nest building process rather than true rejection of the cowbird egg.Excluding these responses,red-wings rejected 15%of cowbird eggs,which is similar to rejection levels from other studies and populations.The overall parasitism frequency on 11 species surveyed in our study area was only 7.4%.Conclusions:Egg rejection behavior does not explain the lack of parasitism on red-wings in our eastern population.Alternatively,we suggest that cowbird preference for other hosts and the low abundance of cowbirds in the east might explain the lack of parasitism.Future research should also explore cowbird and host density and the makeup of the host community to explain the low levels of parasitism on red-wings across eastern North America because egg rejection alone is unlikely to explain this broad geographic trend.
文摘Wallace Stevens is one of five greatest poets in America in 20th century. The relation between imagination and reality is a major theme of his poems. He holds the view that the mission of poets is to build a bridge linking the world of imagination and of reality with the result of deconstructing the logic of binary opposition since the time of Plato. Thirteen Ways of Looking at A Blackbird is a representative poem that expresses Wallace’s thoughts of deconstruction. This article is to probe into how the poet establishes the reality dominated by imagination and then how he deconstructs the binary opposition between imagination and reality since the time of Plato.
文摘This paper reports breeding ecology of Blackbird(Turdus merula mandarinus) in Feixi County,Anhui Province from March to July of 1996.The bird nested in resident quarters earlier than in forests.In the case of breeding in forests,they neted on the trees at the edge of forests near pond.They were compatible with large birds such as heons.The parent-birds attacked violently anyone who contacted their young birds.There were only a few nestlings growing up to leave their nests.Survval rate was determined mainly by weather.The equation of the growth of body weight was W=77 3/[1+e -0 472(t-6 4) ].Compared with the other passerines,such as Blue-winged Pitta and Red-rumped Swallow,nestlings of Blackbird grew up rapidly,leaving their nest with lighter body mass.For the first time,Cuckoo was found laying egg in the nest of Blackbird in China.
