Effects Of Spouse And Paternity Loss On Male Provisioning Investment Of Varied Tit(Sittiparus Varius)

In social monogamous birds,there are different parental investment strategies in the breeding period.Bird parental care is not only a cooperation between male and female,but also a conflict.This is the result of mutual balance between parents.Researchers are interested in how the parent reacts when the other party's input reduces or entirely disappears.Varied tit(Sittiparus varius)is a social monogamous bird and both parents raise the offspring.This study took varied tit as the research object and was carried out in Liaoning Xianrendong National Nature Reserve from2019 to 2020.I experimentally removed the female parent away from its nest for a period during the breeding period and recorded the change of feeding amounts and feeding types of parents,to study the change of the input of male parent in raising the offspring.Given that varied tit has a relatively high proportion of extra-paternity,this study further explored the effect of paternity loss on male investment in breeding the offspring.The results were as follows:1.Under the normal condition of raising the offspring,there was a significant difference in total feeding amount between male and female parents(t=-3.414,P=0.006).The feeding amount of female parent was significantly larger than that of male parent,indicating that the female paid more to the offspring than the male did.2.The male had obvious behavior adjustment after 1 h after spouse removal.There was a significant difference in total feeding amount between before and during spouse removed-period(t=7.529,P<0.001).But the total amount of feeding was not significantly different before and during spouse removed-period(t=0.885,P=0.395).The male fully compensated the input caused by the spouses loss decrease.3.Insects are the main food resources of nestlings,and brood food can be divided into two categories:imago and larva.The composition of brood food of male parents before and after mate removal was not significantly different(X~2=0.114,df=1,P=0.736),indicating that the quality of brood food provided by the male parent did not significantly changed due to mate loss.4.There was no significant difference in the total feeding amount after the spouse return comparing with that before the removal of male parent(t=0.485,P=0.653).This indicates that the male returned to the normal brood state after the return of the mate.5.In normal condition of raising the offspring,the total of feeding comparative difference was not significant with and without extra-paternity copulation offspring(t=0.479,P=0.276).In the case of the female spouse removed,with and without female extra-paternity copulation offspring,the male parent both fully compensate for the decrease of input,and the compensation degree was not significantly different(t=0.138,P=0.160).Thus,male feeding strategy remained the same regardless of extra-paternity copulation.In conclusion,male parents of varied tit have the ability to adjust their breeding strategies flexibly,their reproductive compensation mechanism is complete compensation,and extra-paternity copulation has no effect on these behaviors.