Evolutionary ecology of the variable breeding system of Chinese penduline tits

Although biparental care is the most commonly observed pattern in bird species, the evolutionary causations of variable parental care patterns demand more scientific attention. I investigated the evolutionary ecology of a variable breeding system of the Chinese penduline tits (Remiz consobrinus), in which uniparental, biparental care and biparental desertion of nests occur, and care patterns differ within and between populations, ranging from mainly female-only care to mainly biparental care across populations. To explore the mechanisms of such a flexible parental care system, I used observational, experimental and theoretical methodologies. Within populations, I found that the higher the re-mating opportunities for males, the higher the rate of male desertion. However, re-mating opportunity for females was not associated with female desertion. Across populations, parental care pattern and breeding success of parental care types differed greatly, and revealed that higher male competition intensity and lower offspring survival success may cause biparental care evolved more in one population than the other. Field experiments testing functions of egg burial behaviour found that instead of resolving sexual conflict as that in Eurasian penduline tits, Chinese penduline tits bury eggs to prevent eggs from being blown out of nests. Parents of uniparental care have high parenting capabilities. By temporarily removing the partner of biparental cared nest, I discovered that the remaining partner compensated for the provisioning frequency but not for the brooding duration. The Individual-based simulation revealed that season length and uniparental care efficiency variably affect parental care and lead to polymorphic patterns in a population.