Breeding Habitat Selection And Suitability Evalution Of Scaly-sided Merganser(Mergus Squamatus)

Habitat related research is a relatively basic but very important work in bird research and conservation.Clarifying the relationship between different habitat factors and species is of great significance for bird conservation,especially for rare and endangered birds.The Scaly-sided Merganser(Mergus squamatus)is a global endangered bird species that mainly breeding in the submontane riparian zones of Changbai Mountains in China.Although researches related to the breeding population of Scaly-sided Merganser were started earlier,the limitation of sample size and computer technology lead to a qualitative and vague description for breeding habitat requirements,and there are large discrepancies in the conclusions of some studies,which need to be further confirmed and updated.This study intended to use species distribution models to fit the distribution of potential suitable breeding habitat of the Scaly-sided Merganser and investigate the population size with the model results and field surveys;analysed main factors influenced breeding habitat selection based on regression models in various scales;quantified the responses of human disturbances;verified the mechanism of indicator roles of Scaly-sided Merganser.The results showed that the land cover types is the main factors to effect the distribution of suitable breeding habitat in global scale.The total area of suitable breeding habitats is 43,125km~2,which mainly distributed in southeast Russia(74%)and northeast China(23%),less areas distributed in northeast North Korea(23%).Only 18%suitable breeding habitats are distributed in natural reserves.The population size of breeding Scaly-sided Merganser in Jilin Province was down from 10 years ago(155 pairs vs.140 pairs),but the proportion of non-breeding individuals increased significantly.Six new distribution areas were recorded by this study,but also found that the Scaly-sided was disappeared from five historical ranges.Based on model averaging,the possibility of the Scaly-sided Merganser occurrence increased with the coverage of riparian forests(β=0.07,P=0.01),river width(β=0.09;P<0.01)and proportion of bars(β=0.13;P=0.02).The abundance of Scaly-sided Merganser was increased with the coverage of riparian forests(β=0.02;P=0.02),river sinuosity(β=0.39;P=0.02),river width(β=0.03;P<0.01)and river(β=1.31;P<0.01).And the Scaly-sided Merganser have positive correlations with variety riparian taxon which demonstrated that the Scaly-sided Merganser could use as an effective indicator in submontane riparian zones.Higher habitat complexity of river sections with classic submontane riparian zones characteristics could meet many ecological requirements such as inhabiting,feeding and refuging of the Scaly-sided Merganser.In addition,height of the nest tree(β=0.74;P=0.02),concealment of the nest hole(β=-1.22;P<0.01),canopy cover above the nest(β=0.70;P<0.01)and the river sinuosity(β=0.73;P=0.02)are the main factors effected nest site selection,which showed that the trade-off between predation risk and energy benefit is the main factor in nest site selection decision.Data that were associated with the FID,AD and AT of 42 individual(20 males and 22females)were collected at different locations.Generally,the FIDs were 90.5±22.0 m,ADs were 107.1±18.4 m,ATs were 9.9±8.3 s.A total of 15 fecal samples were analyzed,with mean of glucocorticoid concentration 837.8±99.0 ng/ml.The results showed that individuals who experienced greater levels of human disturbance had shorter FIDs,which indicate that the local population may be habituated to human approach.However,this species spent more time being vigilant in its behavioral budget,which suggested that some other human-induced stimuli may impose negative effects on the species.The results of joint species distribution models showed that the Scaly-sided Merganser had the largest number of positive significant correlations(17 out of 25)with other sympatric bird species and exhibited significant responses to most of the measured environmental variables affecting riparian bird species(5 out of 8).Land cover patches,gravel bar areas,and river width were the most common environmental factors affecting bird species distribution.This result verified the central role of Scaly-sided Merganser as an indicator species in submontane riparian ecosystems due to their strict physical environment preferences and their extensive connections with other sympatric riparian bird species,primarily through shared environmental intersections.The composition of submontane riparian bird communities is affected by both complex environmental variables and biotic interactions.Based on the results of our study,that the current situation of breeding population of Scaly-sided Merganser is not optimistic,and the factors affecting breeding habitat have not been eliminated,so it is necessary to focus on the protection of this species.We suggested that added nature reserves and entrusted the protection function of Scaly-sided Merganser in existing reserves to improve the protection effectiveness of this species;incorporated artificial nest boxes into unified management,and rationally allocate nest spacing according to the abundance of available resources and the number of competitors in the region to reduce nest parasitic phenomena and increase the success rate of reproduction;strengthen scientific research and monitoring,improve the level of protection management,and provide scientific basis for formulating medium and long-term protection plans and strategies;strengthen the protection of habitats,prohibit illegal fishing,sand dredging and other activities to ensure the health of the ecosystem in the mountainous riparian zone,and provide the basis for population expansion of Scaly-sided Merganser.