Alfred Russel Wallace,
The Geographical Distribution of Animals…
“ The Palæarctic element, however, forms so small apportion of the whole fauna, that it may be satisfactorily accounted for by the establishment of immigrants since the Glacial period. The great interest felt by ornithologists in the discovery of the three genera above-named, with a wren allied to a European species, is an indication that the faunas even of the northern parts of the Nearctic and Palæarctic regions are, as regards birds, radically distinct. ”
