Temperature effect on luteinizing hormone secretion of Eurasian Skylark (Alauda arvensis) and Great Tit (Parus major) in China

Abstract 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 °C group was higher than that of those in the 15 °C 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.