Background: Females can differentially deposit the immune factor lysozyme into eggs based on conditions of local breeding density and laying order.Materials: We collected 80 eggs from Great Cormorants(Phalacrocorax ca...Background: Females can differentially deposit the immune factor lysozyme into eggs based on conditions of local breeding density and laying order.Materials: We collected 80 eggs from Great Cormorants(Phalacrocorax carbo) and then analyzed whether the level of lysozymes in the eggs is related to breeding density and laying order.Results: Between clutches,the level of lysozyme in eggs is positively related to breeding density; while within a clutch,the level of lysozyme is positively related to the laying order.Conclusion: When parents breed under conditions of high density,they allocate more lysozymes to their offspring,a trait adaptive to the local environment.That the increase in the level of lysozymes is a function of the laying order seems a necessary condition to mitigate the hierarchy among siblings for improving the survival of the entire clutch.展开更多
Demographic information,such as geographic segregation of sexes and sex ratio data,is needed to develop,model and evaluate conservation and management strategies for wildlife.A variety of physiological,behavioral and ...Demographic information,such as geographic segregation of sexes and sex ratio data,is needed to develop,model and evaluate conservation and management strategies for wildlife.A variety of physiological,behavioral and environmental factors can influence segregation of sexes and sex ratios,many of which originate with density-dependent processes.Departure from 50:50 sex ratios of double-crested cormorants(Phalacrocorax auritus)collected during control efforts in breeding and wintering areas across their eastern range of the USA were evaluated using using a Z-test as well as Stouffer’s weighted Z-tests.In addition,a specifically-designed randomization test was used to evaluate density-dependent effects on primary sex ratios in cormorants from egg collections and colony nest count data over a 21-year period.Cormorants collected from breeding colonies were strongly male-biased,whereas cormorants collected from feeding flocks were slightly biased toward females.Cormorants were partly segregated by sex on the wintering grounds,with significantly more males found in areas with intensive channel catfish aquaculture.The null hypothesis that females produced a balanced sex ratio independent of number of nesting cormorants was rejected:more male embryos were produced during rapid population growth,whereas at maximum nesting number more female embryos were produced.Once populations stabilized,the sex ratio was more equal.This examination of sex ratios indicates that different management methods and locations result in sex-biased culling of cormorants.Sex-biased culling in cormorants could make population reduction efforts more efficient and reduce overall take.We suggest further research to examine density-dependent effects on primary sex ratios documented here.展开更多
基金financially supported by the State Forestry Administration Program (Grant Nos. Y31I351B01)the National Natural Science Foundation of China (Grant Nos. Y011331501)+1 种基金the National Science & Technology Pillar Program (Grant Nos. 2008BADB0B0303)National Basic Research Program of China (Grant Nos. 2010CB530301)
文摘Background: Females can differentially deposit the immune factor lysozyme into eggs based on conditions of local breeding density and laying order.Materials: We collected 80 eggs from Great Cormorants(Phalacrocorax carbo) and then analyzed whether the level of lysozymes in the eggs is related to breeding density and laying order.Results: Between clutches,the level of lysozyme in eggs is positively related to breeding density; while within a clutch,the level of lysozyme is positively related to the laying order.Conclusion: When parents breed under conditions of high density,they allocate more lysozymes to their offspring,a trait adaptive to the local environment.That the increase in the level of lysozymes is a function of the laying order seems a necessary condition to mitigate the hierarchy among siblings for improving the survival of the entire clutch.
文摘Demographic information,such as geographic segregation of sexes and sex ratio data,is needed to develop,model and evaluate conservation and management strategies for wildlife.A variety of physiological,behavioral and environmental factors can influence segregation of sexes and sex ratios,many of which originate with density-dependent processes.Departure from 50:50 sex ratios of double-crested cormorants(Phalacrocorax auritus)collected during control efforts in breeding and wintering areas across their eastern range of the USA were evaluated using using a Z-test as well as Stouffer’s weighted Z-tests.In addition,a specifically-designed randomization test was used to evaluate density-dependent effects on primary sex ratios in cormorants from egg collections and colony nest count data over a 21-year period.Cormorants collected from breeding colonies were strongly male-biased,whereas cormorants collected from feeding flocks were slightly biased toward females.Cormorants were partly segregated by sex on the wintering grounds,with significantly more males found in areas with intensive channel catfish aquaculture.The null hypothesis that females produced a balanced sex ratio independent of number of nesting cormorants was rejected:more male embryos were produced during rapid population growth,whereas at maximum nesting number more female embryos were produced.Once populations stabilized,the sex ratio was more equal.This examination of sex ratios indicates that different management methods and locations result in sex-biased culling of cormorants.Sex-biased culling in cormorants could make population reduction efforts more efficient and reduce overall take.We suggest further research to examine density-dependent effects on primary sex ratios documented here.
