Study On Reproductive Strategy And Conservation Of Relict Gull (Larus Relictus) In Erdos Plateau

The relict gull?Larus relictus?is a rare species breeding at grounds floating and scattering in salt marshes of Asia.It is classified as a vulnerable species by the International Union for Conservation of Nature,as its population only breeds at a small number of wetlands in arid areas which could be strongly influenced by climate change.Currently,changes in water level and loss of ephemeral wetland habitats in semi-arid region of China are imposing an negatively impact on relict gull.To improve the conservation and management of relict gull,we conducted this study to further understand the reproductive strategies and provide the basis for the protection of the relict gulls under the dual pressures of climate change and habitat degradation and the formulation of adaptive management policies for their habitats.This study found that during the period from 1985 to 2011,the climate characteristics of the Ordos Plateau were mainly represented by a increase of annual average temperature,and the precipitation generally showed a decreasing trend.The number of breeding populations of relict gull in Tao-A N ur and Hongjian Nur had little relationship with regional temperature changes,and negatively with the precipitation of the previous year,which indicated that the increase of regional temperature was not a direct factor that restrict the distribution of relict gull.The study on the breeding habitat selection of relict gull found that the structural characteristics of the lake area,such as the available water area in the lake area,the grass area around the lake area and the presence or absence of the lake island,were significantly correlated with the breeding lake selection of relict gull?r=0.853**,P=0.000,n=19?,and water quality characteristics?r=0.079,P=0.749,n=19?and human activities?r=0.069,P=0.779,n=19?were not significantly correlated with this selection process.The nest sites selection of relict gull followed the Ideal Despotic distribution.The coverage and height of vegetations on the islands were important environmental factors affecting the nest sites selection.The relict gulls only choose the vegetation coverage was not higher than 38.9%and the height was not higher than23.15cm.This was related to the charactors of the ground nests.Higher vegetation coverage affects nest building and higher vegetation height affects the vision of birds which in turn affects their observation and defense of predators.Differences in egg weight loss,hatching rate,and hatchling weight caused by different temperature and humidity characteristics in different nest sites between the dry grass and fresh grass areas indicated that the fresh grass area was more conducive to increase the breeding suitability of the relict gull.Based on the calculation of the capacit y index,we found that the main factors limiting the carrying capacity of the relict gull population in Ordos Plateau was food availability.By amplifying 90 microsatellite primers selected from 8 other gulls,we found that 11sites were successfully amplified and polymorphic in the relict gull population.The polymorphism information content was 0.373 to 0.775.The heterozygosity was observed from 0.481 to 0.827.The low amplification rate and polymorphism of the relict gull population at 90 sites compared to other species may indicated that the population had low levels of gene flow and polymorphism.In 2015,the relict gull eggs size ranged from 40.05 cm³ to 66.35 cm³,and decreased with increasing position(F_2,343=35.7,P<0.001);In 2015,the overall offspring sex ratio was 0.549,which was significantly biased towards males?Z=-3.184;P=0.001;n=566?.The sex ratio of first laid egg was significantly biased to males?61 males vs.19 females;Z=-4.696;P<0.001?.Starvation was the dead reason for 98%of the chicks that after 10 days old;The dead chicks over 10-day-old were significantly biased towards males?>10 days;Z=-2.526;P=0.012?.Due to the limited food resources,the egg size maintenance ability of females was poor,and the chicks were severely affected by hunger.These results showed that the breeding group of the relict gulls was in a non-healthy state.Therefore,the managers need to pay attention to the restoration of lake landscapes and other types of wetlands.Some suitable green vegetation are crucial in the construction of breeding islands;Strengthen the management of regional coal mines and salinity production and increase the overall protection of available breeding habitats and the surrounding feeding areas should become current key of wetland ecosystem management in the Ordos Plateau region.