David Sibley has a post up on the distribution of White-crowned Sparrow subspecies. After noticing that one can enter sightings on eBird below the species level (when possible), I’ve been paying more attention to population differences within some species. For example, New Mexico hosts at least four subspecies or subspecies groups of Dark-eyed Juncos, all of which can be identified in the field: Slate-colored, Oregon, Pink-sided, Gray-headed (and sometimes White-winged). Each of these were formerly classified as full species. Even if they are not, recording when and where different population groups of species is important not only to determine distributions but also can help tease out some of the details of speciation and evolution that we are seeing happen before our eyes, although very slowly and not always in one direction.
I’ve been planning to write some blog posts on this very topic, inspired by some earlier blog posts by Sibley on the distribution of some recently split species pairs: Eastern vs Mexican Whip-poor-will and Winter Wren vs. Pacific Wren. I can’t complain about being “scooped” by David Sibley though! Plus, he has some more data to present from the Canadian Atlas of Bird Banding which shows band recovery sites and where each recovered bird was first banded. Keep watching the blog for my own posts on subspecies.
In New Mexico, I have seen both the Gambel’s subspecies and a dark-lored subspecies, almost certainly the one that breeds locally and in the Rocky Mountains.
The eastern and Rocky Mountain subspecies have dark lores and pink bills:
The Northwestern subspecies has an orangey bill and light lores:
Subspecies on the Pacific coast have yellow bills, light lores, and a browner appearance overall (and are resident unlike birds breeding in Canada and the Rockies):