My attempt to associate these implied birds with real species:

There is no smooth-legged hawk, but there is a sharp-shinned hawk. While rough and sharp aren’t quite antonyms, the rough-legged hawk is named for its feathered legs, while the sharp-shinned hawk is named for its long, featherless legs. Don’t ask me, I’m not an ornithologist.

Similarly, no valley chickadee, but the black-capped chickadee overlaps significantly with the mountain chickadee and lives at lower elevations, so I think that’s a pretty good match.

For flycatchers, the best fit is the Short-crested flycatcher, but really there are many flycatchers with crests that are just OK. Honorable mention to the sad flycatcher. Not sure if he’s sad because he doesn’t measure up but I can’t rule it out.

Finally, bitterns. This one is the easiest. The least bittern is, in fact, named with its opposite in mind, which is the great bittern. Poor guy.