Differences between the two species include the amount of white at the base of the lower mandible--all dark in the Long-billed Thrasher, half whitish or yellowish in the Brown. Long-billed Thrashers tend to have darker backs than do Brown Thrashers. Notice the unstreaked undertail feathers on the Long-billed Thrasher. Finally, Long-billed Thrashers have blacker streaking on their underparts than do Brown Thrashers. The Brown Thrasher in the lower photo was taken near Dundas, Minnesota.