On my way into the office this morning I found a Pacific Loon out in the middle of Lake Galena at Peace Valley, visible from the boat launch parking lot on the south side of the lake. Bird has a solid dark gray/brown back so probably an adult. Smaller looking head, thinner neck, smaller more slender and daggerlike bill than Common Loon, straight demarcation between darker back and white front of neck, dark face above white chin and throat. No white visible around eye at my distance (200 yards with 40x scope). Dark back all the way to water line (no white flank patch). Hint of faint chinstrap, at least on right side.
Pacific Loons are only rarely found in Pennsylvania, so this was a great way to start the short work week. Also on the lake were Common Loon and Bonaparte's Gull.