| At present,most researchers have carried out a lot of research on the hot issue of bird breeding,but there is still insufficient evidence to explain the different reproductive strategies evolved in birds.For example,most studies have used body size as a measure to investigate the relationship between body size and reproductive investment,but have found highly variable results between species.Therefore,using body size alone as a reference may not yield the expected results,and the inclusion of additional measures should be considered.For birds with bright plumage coloration,plumage color is often ecologically rich and therefore can be considered an important external biological characteristic of the individual.Previous studies on plumage color have focused on mate choice,but recent studies have found that plumage color can be an important factor and affect their own and even their mate's breeding investments,but some studies have not found this pattern,so further research is needed to determine whether and how plumage coloration can generally affect breeding investments.The varied tit(Sittiparus varius)has bright orange plumage.But the body size of varied tit was not found to be a good indicator of their breeding investment ability in previous studies,and whether plumage color is an indicator of body quality and thus further influences breeding investment deserves further investigation.In the process of parental offspring,the two parents are fraught with conflict despite their apparently cooperative relationship.Both parents want their mates to take on more of the breeding investment.It is still necessary to pay more attention to the coping strategies of the other parent when one parent's investment decreases or disappears,and whether the body condition has an effect on this strategy.In this study,we investigated the correlation between bird plumage color and breeding investments and breeding compensation behavior using experimental methods such as video recording and mates removal in Xianrendong National Nature Reserve in Liaoning Province from 2020 to 2021,using varied tit as the study subjects.The results were as follows.1.Plumage color and parental breeding video data were collected from a total of18 nests of varied tit.The hue,chroma and brightness of the plumage color were extracted from the plumage and the feeding rate,feeding amounts,the proportion of caterpillars and effort per nesting of the parents were analyzed by multiple linear regression.The results showed that the hue of the plumage of males of varied tit was positively correlated with the effort per nesting(n=18,?=0.426,p=0.038)and negatively correlated with the proportion of caterpillars in the food amounts(n=18,?=-0.527,p=0.021),while the hue was correlated with the feeding rate(n=18,?=0.610,p=0.013)and food amounts(n=18,?=0.565,p=0.035),effort per nesting(n=18,?=0.664,p=0.007),and brightness was positively correlated with feeding rate(n=18,?=621,p=0.042);male plumage brightness was positively correlated with female feeding rate(n=18,?=0.820,p=0.041),food amounts(n=18,?=0.876,p=0.040),and effort per nesting(n=18,?=0.836,p=0.032);however,female plumage color did not correlate with either her own or her mate's breeding investment.That is,male plumage color could predict both self and mate breeding investment,while female plumage color did not predict both self and mate breeding investment.2.A total of 28 nests of varied tit were collected after the removal of one parents,of which 16 for removing the female and 12 for removing the male.Results after paired t-tests and chi-square tests showed that when mates were removed,the feeding rate(t=0.872,df=15,p<0.001),effort per nesting(t=0.145,df=15,p<0.001),and food amounts(t=3.124,df=15,p<0.001)of males were significantly higher than before mate removal,but the proportion of caterpillars was significantly decrease(?~2=31.254,df=15,p=0.019),while the male feeding rate(t=0.528,df=15,p=0.221),effort per nesting(t=0.169,df=15,p=0.295),and feeding rate(t=2.911,df=15,p=0.741)did not show a significant decrease compared to the total parental feeding rate(t=0.528,df=15,p=0.221),effort per nesting(t=0.169,df=15,p=0.295)and feeding rate(t=2.911,df=15,p=0.741)before mate removal.but also a significant decrease in the proportion of caterpillars that delivered food(?~2=15.195,df=15,p=0.035).This suggests that after female removal,males could fully compensate for the reduction in feeding rate and total food delivered by female absence,but not the reduction in food quality.In contrast,when the mate was removed,there was a significant increase in female food delivery(t=4.404,df=8,p=0.023),but no change in feeding rate(t=0.950,df=8,p=0.263)or effort per nesting(t=0.176,df=8,p=0.493),but the proportion of caterpillars(?~2=17.128,df=8,p=0.037)showed a decrease;while no significance decrease was observed compared to the total biparental food amounts before mate removal(t=5.411,df=8,p=0.228),the total feeding rate(t=1.450,df=8,p=0.043),effort per nesting(t=0.240,df=8,p=0.041),the proportion of caterpillars(?~2=9.641,df=8,p=0.005)all showed significant reductions.This suggests that female single parent broods were only able to compensate for the absence of males in terms of total food amounts,but not in terms of feeding rate and food quality.3.A total of 16 nests of varied tit were collected for uniparental plumage color and breeding compensation,of which 7 nests were males and 9 nests were females.After Spearman's correlation test,it was found that the plumage coloration was not correlated with the compensation of self and mate breeding.In conclusion,the varied tit has bright plumage,the male flank plumage color can be used as an indicator of its body condition,and the color can affect the breeding investment of itself and its mate,but the female flank plumage color has no effect.The varied tit has reproductive compensation behavior when a single parent is missing.However,the compensation strategies of the two parents are different.The male parent cannot fully compensate for the quality of food,but can fully compensate for the feeding rate and total feeding amount of the whole nest and single chick.The female parent can only fully compensate in the amount of food offered.In addition,plumage coloration is not related with reproductive compensation strategies. |
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