Considered by some authors to be a subspecies of Red Fox-sparrow (Passerella iliaca). References See References. Files: More Information Articles about the Thick-billed Fox-sparrow If you would like to read any articles about the Thick-billed Fox-sparrow... Show Articles (0) No Pictures of Thick-billed Fox-sparrow If Birdpedia has no pictures of Thick-billed Fox-sparrow or you would like to see more, then try the following... From BING (4) No Videos of Thick-billed Fox-sparrow If Birdpedia has no videos of Thick-billed Fox-sparrow or you would like to see more, then try the following.. From BING (0)