Always go check in at the visitor center first, and they will likely tell you where to go if you say you're birding. If they don't, take the trail that goes directly east from the visitor center building. You'll walk through some desert scrub habitat, and the trails eventually curve north. If you continue taking the trails north, you'll have some great river views and eventually end up at a little riparian bosque access. There's a small loop with some benches. This spot is also very near to the pueblo golf courses, which are notoriously difficult for birders and harbor lots of waterfowl in the winter. This is a good spot to watch sometimes hundreds of ducks and geese in the winter as they move around from the golf courses to the river and back.