Wikipedia:Today's featured list/December 7, 2015
There are more than 20 subspecies of the Eurasian nuthatch, a small passerine bird found throughout temperate Asia and in Europe. The Eurasian nuthatch taxa can be divided into three main groups; the S. e. caesia group of Europe, North Africa and the Middle East, the S. e. europaea group (pictured) of Scandinavia, Russia, Japan and northern China and the S. e. sinensis group of southern and eastern China and Taiwan. These may have been geographically isolated from each other until relatively recently. Birds of intermediate appearance occur where the group ranges overlap. The female is usually slightly duller than the male with a brown tint to the eyestripe and paler underparts, although the sexes are very similar in the S. e. sinensis group. The precise number of subspecies depends on how small differences between populations are evaluated. Given the similarities between geographical forms of the Eurasian nuthatch, subspecies boundaries are somewhat fluid, although less than half as many are recognised now as in 1967. (Full list...)