Ranch Road 505 is almost a 9 miles of thin paved road on the Marfa Plain grasslands. The eastern end near TX-166 is slightly undulating coming out of the foothills of the Davis Mountains. It's a mixture of grasslands, Yucca stands and a few small brushy trees that can even hold a Swainson's Hawk nest. In the winter this is a great sparrow habitat. About 2 miles west from the intersection is a Yucca hillside to the south that can support Scott's Orioles and Curve-billed Thrasher. Plus your Golden Eagle may sit on the hill for a view of the plain. The eagles actually can be on this road all year long as some have been known to nest in the nearby high mountains to the north east. At 3 miles from the intersection on the curve to the north is a multi-leveled water tank for cattle. Many birds can be seen around this tank, including Horned Lark, Chestnut-collared Longspur and Common and Chihuahuan Raven. in the winter and migration be on the lookout for flocks of Long-billed Curlew. The western section of 505 is flat and very grassy. A good place to find Northern Harrier flying low. At the railroad tracks on the west end by US-90 to the north is a low spot that can have water for ducks after wet monsoon years. There has been a pair of White-tailed Kite spend a summer on this road before.

Scaled Quail, Greater Roadrunner, Lesser and Common Nighthawk, Upland Sandpiper, White-tailed Kite, Golden Eagle, Northern Harrier, Bald Eagle, Swainson's Hawk, Ferruginous Hawk, Burrowing Owl, Short-eared Owl, Prairie Falcon, Western Kingbird, Chihuahuan & Common Raven, Horned Lark, Cactus Wren, Curve-billed Thrasher, Westen bluebifd, Chestnut-collared Longspur, Cassin's, Grasshopper, Brewer's, & Black-throated Sparrow, Lark Bunting, White-crowned, Sagebrush, Vesper, & Savannah Sparrow. Western & Chihuahuan Meadowlark, Scott's Oriole, Brewer's Blackbird, Blue Grosbeak.