Background:Physiological preparation for reproduction in small passerines involves the increased secretion of reproductive hormones, elevation of the metabolic rate and energy storage, all of which are essential for reproduction. However, it is unclear whether the timing of the physiological processes involved is the same in resident and migrant species that breed in the same area. To answer this question, we compared temporal variation in the plasma concentration of luteinizing hormone(LH), testosterone(T), estradiol(E_2), triiothyronine(T_3) and body mass, between a migrant species, the Eurasian Skylark(Alauda arvensis) and a resident species, the Asian Short-toed Lark(Calandrella cheleensis), both of which breed in northeastern Inner Mongolia, China, during the 2014 and 2015 breeding seasons.Methods:Twenty adult Eurasian Skylarks and twenty Asian Short-toed Larks were captured on March 15, 2014 and 2015 and housed in out-door aviaries. Plasma LH, T(males), E_2(females), T_3 and the body mass of each bird were measured every six days from March 25 to May 6.Results:With the exception of T, which peaked earlier in the Asian Short-toed Lark in 2014, plasma concentrations of LH, T, E_2 and T_3 of both species peaked at almost the same time. However, Asian Short-toed Larks attained peak body mass earlier than Eurasian Skylarks. Plasma T_3 concentrations peaked 12 days earlier than plasma LH in both species. Generally, plasma LH, T, E_2, T_3 and body mass, peaked earlier in both species in 2014 than 2015.Conclusions:The timing of pre-reproductive changes in the endocrine system and energy metabolism can be the same in migrant and resident species; however, residents may accumulate energy reserves faster than migrants. Although migration does not affect the timing of pre-breeding reproductive and metabolic changes, migrant species may need more time to increase their body mass. T levels in resident species may be accelerated by higher spring temperatures that may also advance the pre-breeding preparation of both migra
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.
