Owls of the World: a Photographic Guide

This second edition of a book originally published in 2012 contains data to May 2013.  Aside from 30 new photographs and 70 new or corrected maps there are 19 new species described or split off from previous species, mainly on vocal differences, although the author notes that only 2 of these have so far been confirmed by molecular evidence.  Indeed the main changes since the first edition are that there is much more on the vocalisations of the species, and the use of these for identification purposes.