The delineation of natural areas in New Zealand: Natural areas in the distribution of birds

[First paragraph(s)...]
It became apparent when this seemingly simple project was attempted that distribution maps of birds can be of several different kinds, and that furthermore there are several categories of birds for which they can be used. Thus a distribution map of an introduced species which may still be in the process of extending its range can have little in common with the surviving or relict distribution of a vanishing species. In all, nine different groups and categories were plotted without much success in disclosing a common denominator. There did appear to emerge one or two boundaries which coincided in more than one group, and this particular agreement had something in common with the map here presented, which shows a line approximately along the 38th parallel south latitude and another following in general the mountain divide from East Cape and carried through to include the eastern shore of Stewart Island. West of this line and bounded in the north (roughly) by the 38th parallel, lies the range of distribution of endemic genera of remote affinities and sedentary habits, either very recently extinct or only just surviving. The genera are Stringops, both islands; Turnagra, both islands; Heteralocha, North Island only; and Xenicus, both islands. These boundaries thus appear to have some distributional significance of fairly ancient duration. The same map, with some modifications, could be used to indicate the distribution of a sub-tropical rail (Rallus philipensis) which is well established with continuous distribution as far south as the 38th parallel area, with discontinuous pockets of establishment in Hawke's Bay, Taranaki, Nelson, ? South Westland, and Stewart Island. The whole concept, however, is considered to have strict limitations for detailed definition of areas. On the same map a shaded area has been used to indicate another type of distribution, that of the introduced Australian magpie as worked out in 1945 by L. M. McCaskill (N.Z. Bird Notes 1 :86-104). This is considered to have no direct relation to the other line boundaries shown.