Go out into your yard some night and listen, and you may hear some birds that only come out after dark. One of the most common is the Common Nighthawk (click to hear). This bird flies at dusk and calls frequenly as he feeds on insects. I see and hear it commonly over the downtown areas of towns like Curwensville and Clearfield. In flight, it looks like a brown seagull.
Another bird that will sometimes fly in your neighborhood is the Great Horned Owl. Because of its reclusive habits, you'll be lucky to see this bird, unless you can startle it on its perch during the day. This is the biggest owl you'll find regularly in Pennsylvania, with a wingspan of about five feet. These birds will fly into neighborhoods, over fields, and in the deep forest looking for prey.
You'll have to venture into the woods at night to find the Eastern Screech Owl. This bird makes the spookiest of all nighttime noises. It's a little owl at about 8" high, but makes a big noise. These guys are travellers, moving miles and miles in a single night- you can track their progress across the countryside as the call periodically.
The noisiest of noisy forest birds is the Whippoorwill. These little birds will make their distinctive call for hours on end, sometimes from a single perch. If you happen to camp in one's neighborhood, you may feel like shooing him away after an hour or more of calling! The looks of this bird might explain why they fly at night (well, probably not). But they are one of the ugliest of Pennsylvania birds.