White-throated Sparrow: White or Tan-Striped?


Stephen T Bird
 

On a limb, if I was forced: 1st winter white.

The supercilium is a poor differentiator in basic molt, particularly a late-winter well-sullied adult or 1st winter.
The darker lateral stripe & (apparent) lighter median stripe, sharply contrasting throat & gray cheeks, rufous upper wing suggest a 1st winter white morph to me (which also permits the light breast streaking); but thats all the caveats accepted that winter can be difficult.
Once I've accepted that, I spuriously delude myself into thinking "yeah, that supercilium is fairly light for a 1st winter."

Other's thoughts? Don't take my word for it.


There are not intermediates (to my knowledge). The morph is due to a a gene inversion following a chromosome duplication/introgression likely from Harris Sparrows.
The argument is made, it uniquely has "4 sexes: near-obligate disassortative mating (i.e. a white morph must breed with a tan morph, regardless of each's sex). Almost as interesting as Acorn Woodpecker mating strategies.

-Stephen


On Tue, Mar 9, 2021 at 6:59 AM Sam Zuckerman <samzuckerman@...> wrote:
I photographed a White-throated Sparrow on Rifle Range Trail in Wildcat Canyon Park Monday afternoon and have had a hard time identifying which morph it is. To my eye, the sparrow has features of both. Here's the checklist with photo: https://ebird.org/checklist/S83048389
 
Many thanks for any help on whether this bird is white-striped or tan-striped. I put tan-striped on the checklist, but will change if necessary. 
 
Sam Zuckerman





Sam Zuckerman
 

I photographed a White-throated Sparrow on Rifle Range Trail in Wildcat Canyon Park Monday afternoon and have had a hard time identifying which morph it is. To my eye, the sparrow has features of both. Here's the checklist with photo: https://ebird.org/checklist/S83048389
 
Many thanks for any help on whether this bird is white-striped or tan-striped. I put tan-striped on the checklist, but will change if necessary. 
 
Sam Zuckerman