Research On Frugivorous Birds Feeding Network Structure In Guilin Yanshan Botanical Garden

From August 2020 to September 2021,the fruit composition and characteristics of fleshy fruit plants,the composition of frugivorous birds and the feeding network of fleshy fruit plants in the Guilin Yanshan Botanical Garden were investigated by using line transect,point sample and focus scanning methods.To explore the composition and structure of bird fruit feeding network,the feeding relationship between birds and plants was analyzed to provide basic data reference for the later study of the co-evolution relationship between animals and plants.The specific results are as follows:(1)There are 23 species of fleshy fruit plants(13 orders 18 families),including 14stone fruit,8 berry and 1 aggregate fruit.Most fruit shape is subspherical,ovoid,elliptic and so on.Immature fruit color is cyan,after maturity,more red,black,purple black,etc.There was a significant difference in the number of fruit plants in different months(P<0.001).There were significant differences in fruit length,width,length-width ratio,three-dimensional variance and seed number among different months(P<0.001),but there were no significant differences in fruit weight among different plants(t=8.538,df=22,P=0.069).There were significant differences in seed length,width and length width ratio(P<0.001),and there were no significant differences in seed weight(t=1.697,df=22,P=0.104)and three-dimensional variance(t=0.875,df=22,P=0.391).(2)A total of 20 species of frugivorous birds(2 orders 11 families),19 species of passerine birds,16 species of resident birds and 4 species of winter migratory birds were recorded.In terms of faunal distribution,Oriental species accounted for 60%of the total birds(12),followed by Palaearctic species(5)and widespread species(3).Among the birds,Pycnonotus xanthorrhous was the most numerous(7293)with a density of 19.192hm~2,followed by Zosterops japonicus(5721)with a density of 15.055 hm~2,and Pericrocotus solaris was the least numerous(1)with a density of 0.003(hm~2).The species number,density,diversity and evenness index of frugivorous birds were significantly different in different months(P<0.001).The maximum number of species was 15 in November and December,and the maximum density was 8.7 hm~2in December,The highest diversity index was 2.45 in November,and the highest evenness index was 0.94 in September.There was a significant positive correlation between the number of fruit species(r=0.618,P=0.032),density(r=0.640,P=0.049),diversity index(r=0.578,P=0.025)and the number of fruit species,while the evenness index(r=0.077,P=0.813)had no significant positive correlation with the number of fruit species.(3)20 species of frugivorous birds fed 2340 times(5095 fruits)of 16 plants on trees simultaneously by swallowing and pecking.P.xanthorrhous ate the most plants(16).And Cinnamomum Camphora was the most frequently eaten by frugivorous birds(905)and the most eaten 1771 fruits.The number of fruit eating birds(20 species),plant fruit species(13species),number of links(81)and Network size(260)in autumn and winter are higher than those in spring and summer,so its feeding network is more complex.The Connectance(0.47)and Interaction evenness(0.83)in spring and summer are higher than those in autumn and winter.The research shows that the bird fruit network is a reciprocal network structure with dispersion and asymmetry.There were significant differences in the average number of birds visited,the average feeding time and the average food intake in different months(P<0.001).The average number of visits of frugivorous birds reached the maximum in April was 5.0±3.2 time,the average feeding time reached the maximum in March was 41.5±8.2 s,the average food intake reached the maximum in April was 3.6±3.3 grains/time.There were significant positive correlations between average food intake and body weight(r=0.662,P=0.001),body length(r=0.575,P=0.008),wing length(r=0.487,P=0.029)and beak length(r=0.479,P=0.033),respectively.The height of fruit plants was positively correlated with the number of frugivorous bird species(r=0.672,P<0.001),food intake(r=0.604,P=0.013),feeding times(r=0.620,P<0.001)and visits to birds(r=0.559,P=0.024).There was also a significant positive correlation between breast diameter and species number(r=0.640,P=0.007),food intake(r=0.832,P<0.001),feeding times(r=0.842,P<0.001)and visits to birds(r=0.836,P<0.001).(4)A total of 14 species(2 orders 6 families)of frugivorous birds have been recorded to foraging 711 times and 1687 fruit of Cayratia japonica from October 2020 to January2021.All the birds feed on the trees by swallowing the fruit whole.P.xanthorrhous has the highest feed frequency on C.japonica(185 times),the corresponding relationship is the strongest,it is a key bird species in the seed transmission of C.japonica.The average number of visits to the C.japonica by Pycnonotus jocosus was the largest(3.56±2.07),the average feeding time of the Turdus hortulorum was the longest(26.23±18.51 s)and the average feeding amount of C.japonica was the highest(3.48±2.42).Correlation analysis showed that there was a significant positive correlation between the weigh(r=0.660,P=0.01),body length(r=0.616,P=0.019)and wing length(r=0.574,P=0.042)of frugivorous birds and the average food intake.