| Birds are an important part of the urban ecosystem.In recent years,with the rapid development of urbanization,its influence on birds has caused widespread concern.The early studies on the impact of urbanization on birds mainly focused on the distribution of bird diversity and the change of birds population size in urbanization,nevertheless rare research was done on the strategies of bird population life history,such as the reproductive strategies of birds adapting to urban habitats,Therefore,exploring reproductive strategies of birds adapting to urbanization is of great significance for birds adapting to new urban habitats and evolution.With the continuous development of urbanization,public green space in emerging cities has become an important habitat for birds.Birds have large differences in emerging cities and natural habitats in terms of food resources,predation pressure,and human disturbance.Therefore,this study was intended to explore whether there were different reproductive strategies for Chinese Blackbird(Turdus mandarnus)in different habitats.Based on the background of two different habitats in urban and rural areas,in this study,from March to July of 2017-2018,Nanchang University in Nanchang and the village in Jinyu Town of Yugan County were selected as research sites to investigate the nest site selection,clutch size,hatching process and brooding behavior and reproductive success rate,the main results were as follows:1.The effect of nest site selection on the reproduction of Chinese Blackbird.The results of difference analysis of nest environmental factors showed that the tree height(t=-4.830,df=44,P<0.001),nest height(t=-5.241,df=44,P<0.001),tree ground diameter(t=-4.480,df=44,P<0.001)and percent cover at nest(t=-3.211,df=44,P=0.002)of urban population were significantly lower than those of rural population.Principal component analysis(PCA)indicated that the main determinants of nest site selection were tree height,nest height and tree ground diameter.Poisson regression analysis suggested that nest height(z=3.760,df=30,P<0.001)andminimum spacing of intraspecific nest(z=2.771,df=30,P=0.006)were positively correlated with the reproductive success rate of urban population,while concealment(z=3.281,df=30,P=0.001)and nest depth(z=2.950,df=30,P=0.003)were negatively correlated with the reproductive success of rural population.The more hidden the nest,the easier it is to expose its nest position to the predator.The deeper the nest is,the harder it is for the parent to detect the predator,which means that the higher the concealment,the deeper the nest,the less conducive to the reproduction of the rural population.2.Temperature would not only affect the hatching behavior of Chinese Blackbird but also affect its reproductive success.The average ambient temperature(t=5.177,df=119,P<0.001)and nest temperature(t=4.198,df=119,P<0.001)in urban were significantly higher than those in rural.During incubation period,the time of leaving the nest of urban Chinese Blackbird was significantly longer than that of rural Chinese Blackbird(t=4.585,df=6,P=0.004),while the sitting time was significantly shorter than that of rural Chinese Blackbird(t=6.507,df=6,P=0.001).This was mainly due to the low temperature of nest in rural,which forced the Chinese Blackbird to increase the sitting time to increase the nest temperature.On the other hand,in the nighttime,the nest temperature of Chinese Blackbird was significantly higher than ambient temperature(t=67.605,df=758,P<0.001),while in the daytime the nest temperature was not significantly different from the ambient temperature,which was due to Chinese Blackbird adopted nesting strategy during incubation period.The female born the main hatching task(70.729 %),while the male born the secondary hatching task in incubation period(29.273 %).Conversely,the male born the main brooding task(53.324 %),while the female born the secondary brooding task(46.676 %)in brooding period.When the ambient temperature was low,the gender difference in parental input was more significant,indicating that the temperature would affect the weight distribution of the male and female of Chinese Blackbird.At the same time,low temperature also inhibited the hatching process of eggs.When the nest temperature was lower than 20 °C for more than 39.980 h(n=3),all eggs would failed to hatch.In brooding period,the nesttemperature was lower than 20 °C for more than 13.500 h(n = 1),and the nestling would be die.3.The impact of food resources and predation pressure on the breeding strategies of Chinese Blackbird.Compared with the rural population,the urban population produces fewer,smaller eggs and thinner nest,but the nestling in urban grow healthier than that of in rural because of the richer food in urban habitats.The nest height in urban was significantly lower than that of in rural(t=-5.241,P<0.001,df=44),and the predation rate of the urban population(41.667 %)was higher than that of the rural population(14.286 %),revealing that the higher the nest,the lower predation pressure and human disturbance from the ground.Richer food resources and greater predation pressure have changed the breeding strategy of urban Chinese Blackbird,adopting less and smaller eggs and building thinner nest to reduce early spawning and nesting energy inputs,and more energy was invested in the brooding period to obtain higher quality offspring and thus improve reproductive success.4.The influence of marital breeding on the reproduction of Chinese Blackbird.The nest height of rural population was significantly higher than that of urban population(t=-5.241,df=44,P<0.001),and the number of predators in urban was higher,indicating that rural population faced less predation pressure from the ground.The minimum spacing of intraspecific nest of urban population was greater than that of rural population(z=316,df=44,P=0.052),indicating that the population density of rural Chinese Blackbird population was higher.In addition,the fertilization rate of rural population(89.333 %)was higher than that of urban population(83.333 %),and the ratio of rural population(27.000 %)was also higher than that of urban population(18.420 %).It was explained that the population density of rural population was higher than that of urban population,which increases the chance of extramarital spouses in rural population,and thus improved the fertilization rate.In view of the unique natural habitats in rural,the rural Chinese Blackbird population adopted a breeding strategy of producing more and larger eggs and building thicker nest to increase early spawning and nesting energy inputs.the late brooding energy was invested less,so the rural Chinese Blackbird adopted increased external ratio toincrease the fertilization rate,thereby increasing the reproductive success rate of Chinese Blackbird. |
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