The Big Fill was an engineering project on the First Transcontinental Railroad now located in Golden Spike NHS. To avoid a costly 800 feet tunnel through mountainous terrain east of Promontory Summit, Central Pacific engineers mapped an alternate route that still needed to span a deep ravine. In February 1869, the construction firm of Benson, Farr, & West began construction on a raised bed across the ravine. Over two months, 500 workers hauled more than 10,000 cubic yards of material to build the rail bed. At its extent, the fill extended for 500 feet and up to a depth of 70 feet. A walking trail allows visitors to see the Big Fill via an easy hike. The habitat is mostly shrubsteppe set in a rocky canyon/ravine.
The Big Fill doesn't get a lot of birders. As mentioned on the Golden Spike NHS birding page, most birding is centered around the visitors center and the west grade loop. But a hot spot was created for this specific location which is small and has a very distinct habitat. ROCK WREN are a staple here, and the habitat probably is suitable for CANYON WREN. CHUKAR can be found on the slopes while BURROWING OWL are known to nest here. Other species typical of the area year round include GOLDEN EAGLE, PRAIRIE FALCON, WESTERN MEADOWLARK, and COMMON RAVEN. In the summer months look for LARK SPARROW and SAGE THRASHER here as well. The bird list is small, but its super easy to make a quick stop here on your way into or out of the park.
From I-15 exit 365 head west on UT-13 for 2.5 miles to Corinne. Continue straight onto UT-83 for another 17.4 miles. Turn left following signs onto 7200 North for 2 miles. Follow the slight right as the road turns into 18400 West/Golden Spike Drive for 1.6 miles till you reach the fill on your right.