Although reviews in the birding and ornithological press have often been favourable, there have been criticisms. Peter Kennerley, author and Asian bird expert, considered that some of the illustrations are small and garish or technically inaccurate. He also believes that the over-reliance on sometimes very old museum specimens and dismissal of the wealth of observational data filed by amateur travelling birders is a mistake, and states that many of the taxonomic decisions appear to be random choices, unsupported by published research.