Avian phenotypic convergence is subject to low genetic constraints based on genomic evidence.

"availability of data and materials the analyzed genome sequences are publicly available and were downloaded from the gigascience database ( https://gigadb org/dataset/101000 ; [ 34 ]).; the dna and protein sequence alignments and in-house developed codes used in this study are available in the figshare repository 10 6084/m9 figshare 13175135. availability of data and materials the analyzed genome sequences are publicly available and were downloaded from the gigascience database"

"Competing interests The authors declare that they have no competing interests."

"Funding The study is supported by the internal fund of Academia Sinica. The funding body played no role in the design of the study, data collection and analysis, interpretation of data, or writing of the manuscript."