Sex-biased mortality can occur in birds during development,for example due to sexual differences in energy requirement and/or environmental sensitivity,or the effects of sex hormones or sex differences in the expressi...Sex-biased mortality can occur in birds during development,for example due to sexual differences in energy requirement and/or environmental sensitivity,or the effects of sex hormones or sex differences in the expression of mutations linked to sex chromosomes.The extent of sex-bias in mortality may also be related to environmental conditions that influence offspring development and survival.Urban areas often provide poorer conditions for nestling development resulting in higher offspring mortality compared to natural areas,which may accelerate sex differences in offspring mortality in cities.To test this hypothesis,we examined the sex ratio of dead offspring in Great Tits(Parus major),using 427 samples of unhatched eggs and dead nestlings collected in two urban and two forest sites between 2013 and 2019.The ratio of males in the whole sample of dead offspring(56.9%)was significantly higher than expected by an 1:1 ratio,and the strongest sex biases were detected in urban areas(57.6%males)and in young nestlings(<14 days old,59.0%males).However,the sex ratios of dead offspring did not differ significantly among study sites and between offspring developmental stages.29.3%of unhatched eggs contained a visible embryo,and the proportion of embryo-containing unhatched eggs did not differ significantly between urban and forest study sites.These results suggest male-biased offspring mortality in Great Tits,and highlight the need of large datasets to detect subtle differences between habitats and developmental stages.展开更多
Background: Global warming caused trophic mismatch has affected the breeding success, and even the survival, of some bird species.The ability of birds to accelerate their reproduction onset in the warmer spring could ...Background: Global warming caused trophic mismatch has affected the breeding success, and even the survival, of some bird species.The ability of birds to accelerate their reproduction onset in the warmer spring could be critical to the survival of some species.The activation of the reproductive endocrine axis in birds is a key physiological process that determines the onset of reproduction.Could birds change the HPG axis endocrine rhythm under the temperature rising condition?Methods: Using plasma LH level as an indicator of initiation of the reproductive endocrine and artificially controlling temperature, we compared variations in the timing of activation of the reproductive endocrine axis in response to temperature in two Chinese bird species, the Eurasian Skylark(Alauda arvensis) and the Great Tit(Parus major) at both the population and individual levels.Results: At the population level, temperature only significantly influenced LH level in the Eurasian Skylark, and had no significant effect on the LH levels in the Great Tit.Mean LH level of Eurasian Skylarks in the 20 ℃ group was higher than that of those in the 15 ℃ group throughout the experiment.Large individual variations in the timing of peak LH levels were observed in the high and the low temperature groups of both Eurasian Skylarks and Great Tits.Conclusions: These results indicate that the effects of temperature differ among species.Meanwhile, there appears to be a degree of within population polymorphism in the timing of reproductive endocrine axis activation in some species.This polymorphism could provide the variation required for bird populations to cope with the possible change of their food peak under the climate warming condition.展开更多
The reproductive behaviors of birds are mainly controlled by the hypothalamus-pituitary-gonad axis.Many studies have shown that reproductive hormones are tightly linked to the breeding sub-stages.However,only a few st...The reproductive behaviors of birds are mainly controlled by the hypothalamus-pituitary-gonad axis.Many studies have shown that reproductive hormones are tightly linked to the breeding sub-stages.However,only a few studies have examined the temporal trend of hormone levels among different reproductive stages in multiple brooded species.We investigated the changes in plasma luteinizing hormone(LH)and prolactin(PRL)concentrations during different reproductive stages of the facultative double-brooded Great Tit(Parus major).We found that the concentrations of LH and PRL in females were significantly higher than those in males.Females had significantly higher LH and lower PRL concentrations in the pre-breeding period than in the first/second brooding periods,and there were no significant changes between the first and second brooding periods.The concentrations of LH and PRL in males had no significant difference between the pre-breeding period and the first brooding periods,while LH and PRL concentrations in the second brooding period were significantly higher than those in the first brooding period.We conclude that there are sex-based differences between LH and PRL at different stages of reproduction.The changes in LH and PRL in both males and females should be related to their physiological functions.Especially for males,individuals with higher levels of LH and PRL are more likely to maintain second clutches.展开更多
基金financially supported by the Hungarian National Research,Development and Innovation Office(NKFIH,grant K132490 to AL and grant PD142106 to IP)by the HUN-REN Hungarian Research Network(grant 16007 to AL)by the Sustainable Development and Technologies National Programme of the Hungarian Academy of Sciences(NP2022-II-6/2022)。
文摘Sex-biased mortality can occur in birds during development,for example due to sexual differences in energy requirement and/or environmental sensitivity,or the effects of sex hormones or sex differences in the expression of mutations linked to sex chromosomes.The extent of sex-bias in mortality may also be related to environmental conditions that influence offspring development and survival.Urban areas often provide poorer conditions for nestling development resulting in higher offspring mortality compared to natural areas,which may accelerate sex differences in offspring mortality in cities.To test this hypothesis,we examined the sex ratio of dead offspring in Great Tits(Parus major),using 427 samples of unhatched eggs and dead nestlings collected in two urban and two forest sites between 2013 and 2019.The ratio of males in the whole sample of dead offspring(56.9%)was significantly higher than expected by an 1:1 ratio,and the strongest sex biases were detected in urban areas(57.6%males)and in young nestlings(<14 days old,59.0%males).However,the sex ratios of dead offspring did not differ significantly among study sites and between offspring developmental stages.29.3%of unhatched eggs contained a visible embryo,and the proportion of embryo-containing unhatched eggs did not differ significantly between urban and forest study sites.These results suggest male-biased offspring mortality in Great Tits,and highlight the need of large datasets to detect subtle differences between habitats and developmental stages.
基金supported by the National Natural Science Foundation of China(No.31372225)Fund of Minzu University of China(No.ydzxxk201619)"111" Project(2008-B0844)
文摘Background: Global warming caused trophic mismatch has affected the breeding success, and even the survival, of some bird species.The ability of birds to accelerate their reproduction onset in the warmer spring could be critical to the survival of some species.The activation of the reproductive endocrine axis in birds is a key physiological process that determines the onset of reproduction.Could birds change the HPG axis endocrine rhythm under the temperature rising condition?Methods: Using plasma LH level as an indicator of initiation of the reproductive endocrine and artificially controlling temperature, we compared variations in the timing of activation of the reproductive endocrine axis in response to temperature in two Chinese bird species, the Eurasian Skylark(Alauda arvensis) and the Great Tit(Parus major) at both the population and individual levels.Results: At the population level, temperature only significantly influenced LH level in the Eurasian Skylark, and had no significant effect on the LH levels in the Great Tit.Mean LH level of Eurasian Skylarks in the 20 ℃ group was higher than that of those in the 15 ℃ group throughout the experiment.Large individual variations in the timing of peak LH levels were observed in the high and the low temperature groups of both Eurasian Skylarks and Great Tits.Conclusions: These results indicate that the effects of temperature differ among species.Meanwhile, there appears to be a degree of within population polymorphism in the timing of reproductive endocrine axis activation in some species.This polymorphism could provide the variation required for bird populations to cope with the possible change of their food peak under the climate warming condition.
基金supported by the National Natural Science Foundation of China (No.31770419 and 31971402 to HW,32001094 and 31870368 to JY)
文摘The reproductive behaviors of birds are mainly controlled by the hypothalamus-pituitary-gonad axis.Many studies have shown that reproductive hormones are tightly linked to the breeding sub-stages.However,only a few studies have examined the temporal trend of hormone levels among different reproductive stages in multiple brooded species.We investigated the changes in plasma luteinizing hormone(LH)and prolactin(PRL)concentrations during different reproductive stages of the facultative double-brooded Great Tit(Parus major).We found that the concentrations of LH and PRL in females were significantly higher than those in males.Females had significantly higher LH and lower PRL concentrations in the pre-breeding period than in the first/second brooding periods,and there were no significant changes between the first and second brooding periods.The concentrations of LH and PRL in males had no significant difference between the pre-breeding period and the first brooding periods,while LH and PRL concentrations in the second brooding period were significantly higher than those in the first brooding period.We conclude that there are sex-based differences between LH and PRL at different stages of reproduction.The changes in LH and PRL in both males and females should be related to their physiological functions.Especially for males,individuals with higher levels of LH and PRL are more likely to maintain second clutches.
