Hello everyone, Well this opens up a can of worms that I have a bit to say about. Here's the story that I've pieced together from the literature. This is going to be long-winded and probably disorganized, but hey. The Dark-eyed Junco is highly variable, with up to 15 sub-species being recognized by at least someone. In the southern end of its range there is Junco hyemalis townsendi in S. Baja, and J. h. pontilis in N. Baja. J. h. townsendi is a pale Oregon type, with little sexual dimorphism. They are so gray in color that some authors have put them in the Pink-sided (mearnsi) group, but in reality they are more likely the pale extreme of a cline going south along the Pacific Coast. In central/northern AZ and NM, there's the distinct Red-backed Junco. In the southern Appalachians there's the carolinensis group which are like a big, pale, sedentary Slate-coloreds. Going up the Pacific coast, there are a couple different Oregon types (pinosus, thurberi, montanus, shufeldti, oreganus). Gray-headeds breed through CO and WY and then Pink-sided takes over. In the pine hills of SD and MT, there's the distinct White-winged Junco (aikeni). In the Canadian Rockies, there's the Cassiar's (cismontanus) group that may be a hybrid between oraganus and hyemalis (Slate-colored). And finally, Slate-colored breeds across the boreal forests from AK to NY, interbreeding with carolinensis in WV, VI MD, and s. NY. And of course to the south there are things like the Yellow-eyed, Guadalupe and Volcano Juncos. So, there's tremendous variation going on in this species, which tends to be common throughout its extensive range. Amazingly, genetic research has revealed that this entire set of distinguishable groups has arisen over the past 10,000 yrs following the receding of the most recent glacial maximum. This whole species diverged from the Yellow-eyed Junco and into the various representatives of the species in only 10,000 years. This is really darn fast. Research on a recently (1987) founded population of thurberi Juncos on the UC San Diego campus has revealed that there has been a 20% reduction in the amount of white in the tail compared to birds in the assumed founding population in mountains 70 km away. In 8 generations a major morphological feature was changed by 20%. The songs of these birds has also changed, and their tails and wings have gotten shorter. This shows just how plastic the junco is. In 10,000 yrs, this adaptable species has diverged into this remarkably variable set of sub-species. Nuts. There is one thing that is consistent throughout the range of the species. Where the sub-species meet, there are intergrades. Red-backed Dark-eyed Juncos hybridize with Yellow-eyed Juncos. Red-backeds I think get mis-represented a lot, just like Tony mentioned about Pink-sided. Red-backeds behave, sound, and look more like a Yellow-eyed Junco than their closest Dark-eyed relative, the Gray-headed. But go up to the Kaibab Plateau on the North Rim of the Grand Canyon and you'll find a hybrid population of Red-backed x Gray-headed. Birds in the Chuska Mountians in extreme NE AZ also show signs of hybridization, but they are more similar to Gray-headed than Red-backed. I suspect the same is true in other mountain ranges in N. AZ and NM (Zuni Mtns). I took a trip to the Chuska Mtns and Kaibab Plateau a few years ago with the express intent of looking at these things. Here are some photos: http://www.flickr.com/photos/christian_nunes/ These couple of individuals show the variation in these N. AZ juncos with respects to: Bill Color, Bill Size and Shape, Throat/Breast Pattern, Color on Tertials/Coverts. And where Gray-headed meets Pink-sided in ne. NV, s. ID, ne. UT and s. WY, they hybridize. That's a pretty broad hybrid zone. And there are historical records of hybrid Pink-sided x White-winged in Powder River Co., MT. In 1941, Miller found 3 birds he deemed to be hybrids. Subsequent searches in more recent times haven't found any evidence of hybridization, so if it happens between PS and WW, it's very rare. And this story repeats itself every time one sub-species meets the other, Oregon x Slate-colored, Pink-sided x Oregon, Slate-colored x carolinensis, etc., etc. Overall, Juncos show a lot of variation even within sub-species. Sexual dimorphism is strong within most groups. Things like aberrant features like white wing-bars can be found in many of the sub-species. Miller (1941) found that 2.66% of Slate-colored Juncos had white tips on their wing coverts. He found rates of 1.82% in Pink-sided, and 1.29% in Gray-headed. If you think about how all of these birds came from the same pool 10,000 years ago, it might be implied that any junco has the potential to show a particular phenotype that is more often shown by another sub-species (like white wing-bars). As these birds colonized the mountains of the West, they would expand into new mountain ranges where certain traits became preferable, and divergence occurred. The Red-backed got a dark eye. The Gray-headed had reduced black color in the bill and a darker throat than Red-backed, and they also began to hop rather than walk! And then Pink-sided got pink sides, Oregon took on the dark hood, etc. etc. Sedentary groups like Red-backed, carolinensis, and to some degree White-winged, are larger with bigger bills. The red back became reduced or absent in some groups. But even female Slate-coloreds still have a brown back. The moral of the story is that Juncos are extremely variable, this variability has arisen over the last 10,000 yrs. They poses the ability to be highly plastic, significantly changing their morphology within only a handful of generations. Hybrid zones are common. Can this bird that can change so rapidly really be called separate species? Any taxonomic governing body has to deal with a lot of gray areas here. Red-backed, Guadalupe and White-winged are the most distinct and isolated groups. These, in my mind, are the logical groups to consider elevating to full species status, if any are to be elevated at all. White-winged and Guadalupe are especially isolated with little, if any, influence of other junco genes. My experience with juncos in northern AZ would make me hesitant to raise Red-backed to full species until a more thorough genetic and morphologic study is done on those birds to see if there is any stabilization going on. Although I do absolutely agree with Tony on the similarities between Pink-sided and White-winged, I think that Pink-sided is much more closely related to Gray-headeds in the grand scheme. Maybe White-winged is just an isolated group of Pink-sideds that became isolated X years ago and have diverged into their current distinct selves? It is more logical to me to split off these distinct outliers, and leave the central clump who keep interbreeding as the heart of it all. Climate change will likely continue to drive speciation in this group, and maybe some day they will isolate themselves enough for a nice comprehensive split, but until then I really think we should be patient and enjoy the story as it unfolds. Thanks for reading, Christian NunesBoulder, CO [email protected]
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