Abstract: The process and reason of species divergence is one of the hot issues in evolutionary biology and ecology field, the nature of species divergence is the gene differentiation. This research studied the globally distributed black-crowned night heron. A phylogenetic tree was constructed by using the method of bayesian and maximum likelihood based on mitochondrial COX1 gene. A time tree was built by the BEAST software using a relaxed molecular clock and three calibration points from the divergence time 68.92 million years between Ciconiiformes and Pelecaniformes, 67.12 million years between Ciconiiformes and Sphenisciformes, 72.25 million years between Ciconiiformes and Sphenisciformes. The purpose of this study is to use molecular methods to evaluate the divergence time of black-crowned night heron and infer the divergence factors. The results showed that the night heron could be divided into two lineages according to their distribution areas, the Americas lineage and Asia lineage. The divergence of the two lineages approximately happened 56.74 million years ago. The separation of the Asian continent and America caused this divergence. 

Key words: black-crowned night heron, COX1, phylogenetic relationship, divergence time estimation