Study On The Response Of Reproductive Strategy In Passer Montanus To Environmental Heavy Metal Pollution

Breeding strategy is the basic and important content in the life history of bird,which could easily affect by environmental stresses,such as environmental heavy metal pollution.Environmental heavy metals could easily enrich in bird body through skin,respiration and food chains pathways,leading to body condition decline,clutch size decrease,growth retard of nestlings and investment change of parents,and the like.In the present study,tree sparrow(Passer montanus),a widely distributed and resident small passerine bird in China,was chosen as the study object.Baiyin(BY)district of Gansu province,which has been contaminated by heavy metal pollutions(mainly Copper-Cu,Zinc-Zn,Lead-Pb,and Cadmium-Cd)for more than 60 years,was selected as the polluted study site;Liujiaxia(LJX)district,a relatively unpolluted area and 110 km apart from BY,was chosen as the control site.The breeding processes of tree sparrow from both sites were continuously monitored during the breeding season of 2017 to 2019.The study mainly monitored: the heavy metal accumulation levels in female and male adults,nestlings and eggs;body condition of parents and growth of nestlings;parental behavior characteristics during incubation and nestling periods;clutch size,egg characteristics and trade-off strategy,and so on.Through the above studies,the aim of this dissertation is to illuminate effect of environmental heavy metal pollution on the reproductive strategy of tree sparrow.The main results are shown as follows:1.Heavy metal concentrations in tissues and organs of adult and nestling tree sparrows and feces of nestlings from BY and LJX.The concentration test results of Cu,Zn,Pb,Cd and Ca in primary feathers(the first and fifth primary feathers of each wing),livers,kidneys,muscles,skeletons of adults and nestlings and feces of nestlings showed: in the tissues and organs of adults in the same site,Cu and Cd were mainly accumulated in kidneys,Zn and Ca were mainly accumulated in skeletons,Pb was mainly accumulated in feathers and skeletons,while five metal elements were mainly accumulated in feathers and skeletons of nestlings;except the concentrations of Ca in feathers of adults and nestlings in BY were significantly lower than that in LJX,the other four heavy metal concentrations in feathers in BY were significantly higher than that in LJX;the concentrations of Pb and Cd in livers,kidneys,muscles,skeletons of adults and nestlings in BY were significantly higher than that in LJX,but Ca concentrations in skeletons of nestlings were significantly lower than that in LJX;the five metal concentrations in nestling feces in BY were all significantly higher than that in LJX.These results indicated that heavy metals would significantly accumulate in tree sparrow under environmental heavy metal pollution.2.Heavy metal concentrations in eggs of tree sparrow from BY and LJX.The concentration test results of Cu,Zn,Pb,Cd and Ca in the non-embryonated(no visible embryo present in the yolk)and embryonated(a visible embryo present in the yolk)eggs showed: the five metal concentrations in eggshells were all significantly higher than those in egg contents in the same site,while the concentrations of Cu,Pb and Cd in eggshells of embryonated eggs were significantly higher than those of nonembryonated eggs,Ca concentrations in egg contents of embryonated eggs were significantly higher than those of non-embryonated eggs;Cu concentrations in eggshells of non-embryonated eggs and Pb concentrations in eggshells of embryonated eggs in BY were significantly higher than that in LJX,Pb and Ca concentrations in egg contents of embryonated eggs were significantly higher than that in LJX.These results indicated that eggshells were easily to accumulate heavy metals than egg contents of tree sparrow,and heavy metals would significantly accumulate in eggs under environmental heavy metal pollution.3.Effects of environmental heavy metal pollution on reproductive characteristics of tree sparrow.The results of body condition of parents,clutch size,hatching rate,fledglings,and fledgling rate showed: no significant difference was found in body condition of parents between BY and LJX;the clutch size in BY was significantly smaller than that in LJX,and a negative correlation was found between clutch size and Cd feather concentrations of females in BY;no significant difference was found in hatching rate between BY and LJX,but fledglings and fledgling rate in BY were significantly lower than that in LJX,and incubation period and nestling period in BY were longer than that in LJX.These results indicated that the reproductive characteristics of tree sparrow should be affected under environmental heavy metal pollution.4.Effects of environmental heavy metal pollution on growth of nestling tree sparrows.The results of body parameters,body condition and growth rates of nestlings showed: the body parameters of nestlings in BY were significantly smaller than that in LJX,but no significant differences were found in body condition of 10-day-old nestlings and growth rates of nestlings between BY and LJX;wing and tarsometatarsus growth rates were negatively correlated with Pb and Cd concentrations of nestlings in BY.These results indicated that the growth of nestling tree sparrows should be affected under environmental heavy metal pollution.5.Effects of environmental heavy metal pollution on parental investment of tree sparrow.The results of incubation temperature,incubation duration,incubation visits and feeding visits showed: no differences were found in incubation temperature,incubation duration and number of feeding visits between BY and LJX,but number of incubation visits in BY were significantly higher than that in LJX;with incubation progress prolonged,incubation duration and incubation visits in BY were decreased;incubation duration and incubation visits were negatively correlated with Pb and Cd feather concentrations of parents in BY.These results indicated that the incubation behavior of tree sparrow was changed under environmental heavy metal pollution.6.Effects of environmental heavy metal pollution on egg size and eggshell thickness of tree sparrow.The results of egg volume,within-clutch coefficient of variation for egg volume and eggshell thickness showed: clutches containing four eggs in LJX had significantly higher egg volume compared to BY;no significant difference was found in within-clutch coefficient of variation for egg volume between BY and LJX;egg volume and within-clutch coefficient of variation for egg volume all increased with clutch size in BY,and within-clutch coefficient of variation for egg volume was positively correlated with Zn and Pb eggshell concentrations in BY;eggshells of nonembryonated eggs were thicker than that of embryonated ones in the same site;the eggshells in LJX were thicker than that in BY for both non-embryonated and embryonated eggs.These results indicated that egg size and eggshell thickness decreased,and a trade-off happened between clutch size and egg size of tree sparrow under environmental heavy metal pollution.7.Effects of environmental heavy metal pollution on eggshell coloration and eggshell spotting pattern of tree sparrow.The results of lightness,chroma,hue and spotting coverage ratio of eggshells showed: the lightness and hue of eggshells in BY were significantly lower than that in LJX,but no significant differences were found in chroma and spotting coverage ratio between BY and LJX;the spotting coverage ratios of blunt poles of eggshells were positively correlated with Zn and Pb eggshell concentrations in BY,and a positive correlation was found between spotting coverage ratios of blunt poles of eggshells and Pb eggshell concentrations in LJX.These results indicated that darker eggshell coloration and aggregated spotting distribution of tree sparrow were formed under environmental heavy metal pollution.In conclusion,the present results explored that environmental heavy metals could easily accumulate in tissues and organs of adults and nestlings of tree sparrow,and had significant effects on the growth of nestlings;the accumulation of heavy metals in eggs would affect development of embryos;the stress of environmental heavy metals could cause significant change in reproductive characteristics,mainly found clutch size and fledglings decreased,fledgling rate declined and incubation visits increased;the characteristics of eggs also changed significantly under environmental heavy metal pollution,mainly found eggshell thickness decreased,eggshell coloration darker and spotting distribution more aggregated.In a word,long-term environmental heavy metal pollution would significantly affect the reproductive strategy of tree sparrow,and the results could provide reference for further exploring the variation mechanism of reproductive strategy and diversity protection on birds.