Monday, 1 April 2013

RE: [cobirds] status of "Red-backed" Junco in Colorado

Dave et al.,

I used to live in Flagstaff, AZ, which is where I first started getting interested in juncos when an intergrade Red-backed/Gray-headed showed up at my feeder. Before I get into this, I'd like to point out that an intergrade is a cross between two distinct races of a single species, while a hybrid is a cross between two species. 

Red-backed is the breeding sub-species on the Mogollon Rim region of central and northern AZ, and central NM. They are rare breeders in the Guadalupe and Davis Mtns of TX. Red-backed x Yellow-eyed Juncos have been found in the Guadalupe Mtns (also a population of those hybrids in southern NM and a record from the Pinal Mtns of AZ). 

As others have mentioned, Red-backed has a larger bill the should be strongly bi-colored. The amount of duskiness in the upper mandible varies a lot. They often look flat-headed to me, probably because their skulls are shaped differently to support the larger bill. They also have more extensive rust color, bleeding from the back onto the wing coverts and tertials (beware HY tertials that are edged with brown). They have a pale throat and breast. To my eye, they are distinctly larger than other juncos typical to that region, akin to a White-winged. They walk rather than hop. Their song is often much more complex than a typical Dark-eyed, closer to a Yellow-eyed. 

When I look at Gray-headeds here in CO, I often notice pale-throated individuals. Birds with a bit of duskiness in the upper mandible are also regular. Almost all have at least a bit of duskiness around the nostrils and at the very tip of the upper mandible. These features, by themselves (or even together), aren't a sign of intergradation, just a bit of the normal variance in the population. But when you get a big honkin' Gray-headed type with a completely dark ridge on the upper mandible, a pale throat and breast, and with some rust on the wing coverts, red flags should go up. 

I think that Steve's photo from Red-rocks demonstrates a very good example of Red-backed genes making it up this far north on the Front Range. The bill pattern is nearly perfect for a Red-backed. The bill size and head shape are spot-on for a Red-backed. It does have a pale throat. It's hard for me to pull the trigger and call it a flat-out Red-backed just because of the precedence. It's more likely that it came up from one of the intergrade zones in central NM. 

There are large areas where Red-backed and Gray-headed swap genes. I think it is a dynamic process. Gray-headeds bop south sometimes, Red-backeds bop north a bit. There's a lot to shake these things up, most notably these catastrophic wildfires. 

Here are some photos to ponder:

Gray-headed from Colorado:

Red-backed from Flagstaff, AZ:

Gray-headed type from the Kaibab Plateau, AZ (intergrade zone): 

Red-backed x Gray-headed types from the Kaibab Plateau, AZ (intergrade zone):

Gray-headed x Red-backed type from the Chuska Mountains of NE AZ (intergrade zone):

The birds on the Kaibab Plateau, which is on the North Rim of the Grand Canyon, area an intergrade population of Red-backed x Gray-headed. The birds in the Chuska Mtns of extreme NE Arizona are of arguable heritage. Some authors think they're all Gray-headeds, some think they're intergrades. When I visited there a few years ago to look at them in the flesh, I found them to be mostly Gray-headed with a few intergrades.

When I visited the Kaibab Plateau, most of the juncos I found were Red-backed x Gray-headed intergrades, leaning more towards Red-backed in looks. I found one that looked like a typical Gray-headed. There has been a recent study of a hybrid population of Red-backed x Yellow-eyed in NM (unpublished). They also found that the occasional Gray-headed would set up territory, well south of where one should be. 

The birds in the Sandia Mtns tend to show intergrade characteristics, although I think most people consider them to be "Gray-headeds". If you travel west from Albuquerque, once you hit some good pine forest, you should find intergrades. It doesn't surprise me that Red-backed genes are flowing up to the Sandias, and possibly further north. 


Good juncoing,

Christian Nunes
Boulder, CO
pajaroboy@hotmail.com





From: daleatherman@msn.com
To: peterburke@gmail.com; cobirds@googlegroups.com
Subject: RE: [cobirds] status of "Red-backed" Junco in Colorado
Date: Sun, 31 Mar 2013 22:21:12 -0600

Peter et al,
The bird at Red Rocks was photographed by Steve Mlodinow, not me.  Unfortunately I got no photos of the recent Crow Valley bird.  In his post, Steve said the Red Rocks bird was a good candidate for a hybrid between Red-backed and Gray-headed.  The other marks (besides the bill color feature you mentioned) stated in the literature are bill size (R-b a bit bigger than G-h) and pale throat and upper breast (that in R-b contrasts with the rest of the darker gray underparts, with G-h being uniformly gray underneath).

Dave Leatherman
Fort Collins

Date: Sun, 31 Mar 2013 22:06:26 -0600
Subject: Re: [cobirds] status of "Red-backed" Junco in Colorado
From: peterburke@gmail.com
To: zebrilus@gmail.com
CC: cobirds@googlegroups.com

Doug & Cobirds,
Since we're on the topic of Red-backed vs. Gray-headed Juncos, the field mark I've been relying on is bill color: single color for Gray-headed, bi-colored in the case of Red-backed. My question is whether this character is diagnostic or not? The Junco David photographed at Red Rocks was sporting a bi-colored bill...

Good birding,
Peter Burke
Boulder, CO


On Sun, Mar 31, 2013 at 8:31 PM, Doug Faulkner <zebrilus@gmail.com> wrote:
David,

The Colorado Bird Records Committee does not have any record for that subspecies and I am unaware of any extralimital reports for other states north of its range.  My understanding is that Red-backed Junco does very little (if any) seasonal movement in a way that would be considered migration.  However, species that might be grouped in that category, like Greater Roadrunner and Canyon Towhee, occur out of range more frequently (and at quite some distance) than their non-migratory status would imply.   Due to its similarity with Gray-headed Junco, it's conceivable for Red-backed Junco to have occurred in the state and gone unnoticed.

Thanks for bringing this topic to our attention.  I for one will be thinking about this possibility anytime I come across a "red-backed" junco on the eastern plains.

good birding,

Doug Faulkner
Arvada, CO



On Sun, Mar 31, 2013 at 12:30 PM, DAVID A LEATHERMAN <daleatherman@msn.com> wrote:
The other day, buried amid a mixed-subject post, I asked (so far unanswered) if anyone on this listserv knows whether the so-called "Red-backed" Dark-eyed Junco has occurred in Colorado and/or whether it has any history whatsoever of occurring outside its normal range of Arizona to West Texas.  This subspecies is Junco hyemalis dorsalis and is considered distinct from our reddish-backed breeder in CO (aka the "Gray-headed Junco, J. h. caniceps).   I had a junco with a bright red back patch at Crow Valley the other day that "looked different" and it just got me to wondering about this junco subspecies.  Thanks.

Dave Leatherman
Fort Collins

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