DNA barcoding uses short DNA sequences from a standardized genome region to identify species. This study tested the effectiveness of a COI barcode in distinguishing bird species. COI barcodes were determined for 260 North American bird species, revealing that each species had a unique barcode, with significant differences between closely related species. The study identified four probable new bird species, suggesting that a global survey could reveal many more. COI barcodes proved effective for bird species identification, with sequence differences between species being 18 times higher than within species. This supports the use of a standard threshold (10× average intraspecific difference) for identifying new species. The study highlights the potential of DNA barcoding as a tool for species identification, with applications in taxonomy, conservation, and ecological research. A comprehensive library of COI sequences linked to named specimens is being assembled to enhance species identification. The research underscores the importance of DNA barcoding in understanding biodiversity and species diversity, particularly in cases where morphological identification is challenging. The study also notes the need for further research to address issues such as hybridization and the potential for underestimating intraspecific variation. Overall, DNA barcoding offers a powerful and efficient method for species identification, with implications for global biodiversity studies.DNA barcoding uses short DNA sequences from a standardized genome region to identify species. This study tested the effectiveness of a COI barcode in distinguishing bird species. COI barcodes were determined for 260 North American bird species, revealing that each species had a unique barcode, with significant differences between closely related species. The study identified four probable new bird species, suggesting that a global survey could reveal many more. COI barcodes proved effective for bird species identification, with sequence differences between species being 18 times higher than within species. This supports the use of a standard threshold (10× average intraspecific difference) for identifying new species. The study highlights the potential of DNA barcoding as a tool for species identification, with applications in taxonomy, conservation, and ecological research. A comprehensive library of COI sequences linked to named specimens is being assembled to enhance species identification. The research underscores the importance of DNA barcoding in understanding biodiversity and species diversity, particularly in cases where morphological identification is challenging. The study also notes the need for further research to address issues such as hybridization and the potential for underestimating intraspecific variation. Overall, DNA barcoding offers a powerful and efficient method for species identification, with implications for global biodiversity studies.