Study On The Factors Of Reproductive Investment In Great Tit(Parus Major)

Reproductive behaviors and activities during bird reproduction are critically important to the development of the population.The higher cost parental care represented by feeding rates directly affects the individual's fitness benefits.Therefore,there may be a conflict of interest between the spouses,because everyone wants his partner to invest more.The changes in breeding strategies caused by the conflict between the sexes and the adaptation strategies of species under specific circumstances have become hot topics in the study of bird behavior in recent years.We observed and recorded feeding behaviors of the great tit parent birds from April to June,2017 to investigate the effects of body quality,the input of nesting,spawning and hatching input,breeding frequency,and climatic factors on the biparental brooding of great tit in the first and second reproduction.The results are as follows:The great tit bred twice a year.The first reproduction is concentrated in April 11 to 28,and the secondary reproduction is from May 28 to June 22.Sixty nests breeding tits were collected and 31 of them had successfully reproduced.The clutch size was 8~13 with an average of 10.85±0.16(n=60);the brooding time was 13~16 days with an average of 14.36±0.19 days(n=37);the number of nestling was 6~12 with an average of 9.48±0.32(n=35),and the hatching rate was 58%~100%(n=35);the feeding period was 16~22 days with an average of 18.29±0.28 days(n=31).The weight of nested materials was 18.874~61.830 g with an average of 34.64±11.51g(n=31).There was no significant correlation between feeding frequency of male and female birds in the first breeding reproduction,and the feeding frequency of male was significantly higher than the females.In the first breeding of great tit,the feeding rate of female parent birds increased with the increase of their width and spouse's width,while the feeding rate of male birds was not related to their physical signs or their physical signs.The feeding rate of female parents was significantly increased with the higher hatching rate and later date of the first egg,and they would adjusted the feeding rate according to the weight of the early chicks: the larger weight of the early chicks,the higher feeding rate of the females at the later stage.The female parent would also adjust the investment according to the input intensity of their spouse,the more they input,the less they invest in the later period,which is in line with the reproductive compensation hypothesis.The climatic factors had no significant effect on the feeding frequency of great tit in one breeding brooding period.A total of 21 nests of secondary reproduction were collected,of which 11 were successfully.The clutch size was 6-10,with an average of 7.81±0.31 pieces(n=17);the incubating period was 12-15 days,with an average of 13.75±0.36 days(n=16);the nestling was 4-9,with an average of 6.77±0.43(n=17);the hatching rate was 75% to 100%(n=17);the brooding period was 17 to 21 days,with an average of 18.57±0.29 days(n=14);the weight of the nest material was 15.10 g to 54.40 g,with an average of 31.21±12.46 g(n=14).The total investments in secondary reproduction were lower than that of first reproduction.There was a significant negative correlation between feeding frequency of male and female parents,and their feeding frequencies were not related to their own physical signs or partner signs.In the secondary reproduction,the parental performance was just opposite to the first breeding.The male parent bird would increase the food supply as the hatching rate increases,while the female parent bird had no adjustment.There was a significant negative correlation between the feeding rate in the late brooding period of male bird and the weight of the early chicks.The male parents would dynamically adjust the feeding rate according to the temperature,and higher temperature resulted in higher feeding rate.There were 5 parents that successfully bred in first and secondary reproduction.The feeding rates of parental great tits were not affected by the nesting,spawning,and hatching investment in first reproduction.In summary,the great tit in Liaoning province breeds twice a year.The investment in secondary reproduction was lower than that of primary breeding.In the first reproduction,the parental investment strategy was different: females would dynamically adjust feeding frequency according to the nestling needs,while males provided a higher stable feeding frequency,and the parental investment was in accord with the breeding compensation hypothesis.The brooding strategy of the second-reproduction was exactly the opposite.Males would dynamically adjust the feeding frequency according to the nestlig needs at different periods and climatic factors,while females provided lower stable feeding frequencies.