miRNA annotation and expression analysis in zebra finch. (A) Mature sequences, expression counts, and precursor sequences with predicted hairpin-like secondary structures of three novel miRNAs identified in the zebra finch. Nucleotides labeled in red and blue in the precursor sequences represent mature miRNAs and their star sequences, respectively. The read numbers are combined from four tissues and two sexes. (B) Relative percentages of small RNA populations among the total sequence reads. Calculations were based on the total reads of the eight libraries combined. (C) The 20 most abundantly expressed miRNAs.