Study On Selection Of Artificial Nest Boxes And Nest Structure Of Urban Oriental Magpie Robin Copsychus Saularis

Urbanization has led to a scarcity of nest resources for secondary cavity-nesting birds in cities.Therefore,providing them with artificial nest boxes could help improve their reproductive success,as well as provide us with an opportunity to study the reproductive biology of urban birds.So far,the use of artificial nest boxes is mostly limited to natural habitats,and researches on the life history of birds usually focus on the brooding period with high food demand,while lacking researches on nesting behavior.In this study,we monitored the reproduction process of Oriental Magpie Robin(Copsychus saularis)attracted by artificial nest boxes in Qianhu North District of Nanchang University,Medical College of Nanchang University and Nanchang Hangkong University,Nanchang City,Jiangxi Province from March to July in 2020-2022.Based on the methods of correlation analysis,difference comparison and generalized linear model,we discussed the artificial nest boxes and nest structure selection strategies of the urban secondary cavity-nesting birds.The main results and conclusions are as follows:(1)A total of 1221 artificial nest boxes were hung during the period,attracting209 nests of 5 breeding bird species,including 189 nests of Oriental Magpie Robin(90.43%),17 nests of Great Tit(8.13%),1 nest of Red-Billed Starling(0.48%),1 nest of Chinese Blackbird(0.48%)and 1 nest of Crested Myna(0.48%).The utilization rates of artificial nest boxes in 2020,2021 and 2022 were 5.83%,22.70%and 16.83%,respectively.No significant difference was found in the utilization rate of large nest boxes(16.17%)and small nest boxes(15.21%)by Oriental Magpie Robin(χ~2=0.210,P=0.647).There were significant differences in the utilization rates of nest boxes on artificial green belts(17.42%),secondary forests(8.29%)and artificial buildings(8.16%,χ~2=11.811,P=0.003).There was no significant difference in the utilization rate of artificial nest boxes on evergreen broad-leaved trees(16.10%),deciduous broad-leaved trees(15.04%)and evergreen coniferous trees(16.36%,χ~2=0.104,P=0.949).No significant difference was found in the utilization rate of artificial nest boxes with different hole orientations(χ~2=9.937,P=0.192).Oriental Magpie Robin preferred to choose nest boxes with higher nest height(P=0.007),lower concealment within 100 cm(P<0.001),farther distance to the water sources(P=0.010),and higher urbanization levels(higher small-scale urbanization scores(P=0.009)and large-scale urbanization scores(P<0.001)).The best model(AICc=979.450,ΔAICc=0.000,ω_i=0.556)showed that Oriental Magpie Robin tended to choose nest boxes locations with low concealment within 100 cm,far distance to the water sources and high urbanization scores.These factors are key factors affecting nest box selection of Oriental Magpie Robin.Nest box selection of birds is a complex decision that is influenced by predation risk,food resources and other factors.Firstly,birds respond to nest predation by choosing nest boxes with higher position but lower concealment.Nest boxes with higher position reduces the risk of ground predation,while lower concealment allows birds to detect and utilize them in time.Secondly,birds choose nest boxes located in artificial green belts or with high small-scale urbanization scores to be closer to abundant food resources and to reduce predation risk by being closer to humans.(2)The short diameter of the nest(P=0.003),lining thickness(P=0.027),distance from the hole(P<0.001),total nest weight(P<0.001),lining weight(P<0.001)and moss weight(P<0.001)of nests in large nest boxes were significantly higher than those in small nest boxes.In large nest boxes,the nest depth of successful nests was significantly lower than that of failed nests(P=0.017).Nest depth were significantly positively correlated with body weight(P=0.015)and tarsus length(P=0.004)of parent birds.Nest depth(P=0.032),lining thickness(P=0.020),moss thickness(P=0.007),total nest weight(P=0.045)and moss weight(P=0.048)were significantly negatively correlated with egg-laying date.Lining thickness(P=0.015)and total nest weight(P=0.035)were positively correlated with clutch size.In small nest boxes,nest depth(P=0.004)and lining thickness(P=0.016)of successful nests were significantly lower than those of failed nests.Nest depth was significantly positively correlated with body length(P=0.002)of parent birds.Nest depth(P=0.002)and lining thickness(P=0.027)were significantly negatively correlated with egg-laying date.Moss thickness(P=0.040)and total nest weight(P=0.024)were significantly negatively correlated with clutch size.The nest size of urban secondary cavity-nesting birds is influenced by the size of their body and nest boxes.The larger the body size,the larger the nest,and the larger the nest box,the larger the nest.Urban birds are able to assess environmental conditions and adjust nest structures accordingly based on egg-laying date to cope with the rising environmental temperature,so as to create the optimal microenvironment for offspring.They also reduce energy investment during incubation period by improving nest insulation and allocate more energy to laying larger clutch sizes.Additionally,in urban habitats with higher ambient temperatures,smaller and thinner nests are favorable for reproductive success.(3)We propose corresponding protection suggestions for the conservation of urban bird resources in future urban development.Firstly,artificial nest boxes can be provided to compensate the shortage of natural nest cavities and improve the breeding opportunities of secondary cavity-nesting birds.Secondly,the hanging scheme of artificial nest boxes can be improved to avoid"ecological traps",such as hanging the nest boxes on tall trees and ensuring a sufficient open view in front of the nest boxes.Finally,regular bird resource surveys should be conducted to understand the status and changes of resources,so as to carry out scientific bird resource management.