Do migrant and resident species differ in the timing of increases in reproductive and thyroid hormone secretion and body mass? A case study in the comparison of pre-breeding physiological rhythms in the Eurasian Skylark and Asian Short-toed Lark

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 migrants and residents.

Using stable isotope to compare the habitat use and trophie level between the new and old breeding range of wild Crested Ibis in the early breeding season

The concept of foraging niche provides an insight into habitat use and dietary information of animals.Knowing intraspecific variation in foraging niche and trophic level is critical to the understanding of the species response to environmental changes during the process of range expansion,as well as the habitat management for conservation of threatened species.Using stable isotopic values of eggshell membranes(δ;C andδ;N),we examined whether there are differences in habitat use,trophic level,foraging niche width between the new and old breeding habitats(plains vs.mountains)of wild Crested Ibis(Nipponia nippon)in the early breeding season.Crested Ibis exhibited high variability in bothδ;C andδ;N values,δ;C andδ;N varied as a function of habitat types.Birds breeding in plains had significantly higherδ;C but lowerδ;N values compared to the birds breeding in mountains.Higherδ;N suggested that individuals in mountains consumed a great proportion of higher trophic level prey species in the early breeding season.Moreover,the isotopic niches were distinctly different in positions and showed small overlap between the two habitat types.The niche width was wider in old habitat than in the expanded new habitat.Our results demonstrated that the wild Crested Ibis had a high intraspecific variation in habitat uses and trophic levels in the early breeding season,and they could be divided into mountain and plain groups based on their different foraging niches.The difference inδ;N and niche width revealed that high trophic level food resources might be insufficient in plains.These findings stressed the importance of protecting foraging grounds in mountains and the necessity of improving foraging grounds in plains during winter and spring.Our study highlights the feasibility of investigating intraspecific variation in foraging ecology of birds through non-invasive isotopes of eggshell membranes.Understanding foraging niche variation gives us an insight into the food resource diversity in local areas and provides important information regarding particular foraging habitats that require protection.

Analysis of key microbial community during the start-up of anaerobic ammonium oxidation process with paddy soil as inoculated sludge

A sequencing batch reactor（SBR）-anaerobic ammonium oxidation（anammox） system was started up with the paddy soil as inoculated sludge. The key microbial community structure in the system along with the enrichment time was investigated by using molecular biology methods（e.g., high-throughput 16 S r RNA gene sequencing and quantitative PCR）. Meanwhile,the influent and effluent water quality was continuously monitored during the whole start-up stage. The results showed that the microbial diversity decreased as the operation time initially and increased afterwards, and the microbial niches in the system were redistributed. The anammox bacterial community structure in the SBR-anammox system shifted during the enrichment, the most dominant anammox bacteria were Candidatus Jettenia. The maximum biomass of anammox bacteria achieved 1.68 × 10~9 copies/g dry sludge during the enrichment period, and the highest removal rate of TN achieved around 75%.