Mary & I found this Parasitic Jaeger at Rimrock Lake Saturday morning, September 28, 2013.

Neither of us had ever seen a jaeger before. It is a light adult. It took us a little while to settle on the identification. Flying, the central tail feathers are a bit longer than the others, protruding distinctly. White showed on the wing primaries' dorsal surface. White triangles in the underside of the wings' primaries are prominent, ruling out Long-tailed Jaeger, which have dark underwings. The bill is not two toned, and the dark brown hood doesn't come down under the bill, as in Pomerine Jaeger. There is a bit of what appears to be loose or shedding keratin on the top of the upper mandible. The jaeger was noticeably smaller than California Gulls, one of which harassed it, a surprise. I'd thought the other way around more likely.
Mike & Alice Roper arrived soon after and joined us in watching it, along with the adult Sabine's Gull that Luke Safford found a few days ago.
The only previous notation I've found of a Parasitic Jaeger in Yakima County is a mention of one in Andy Stepniewski's book, "The Birds of Yakima County, Washington". In the Parasitic Jaeger account Andy wrote,
""One...harassing terns over the Columbia River 7 miles south of Beverly on June3, 1979" (AB 33:882) was presumably a spring migrant and is the only report for Yakima County."

Yakima County bird records stuff:

Beverly is 7 miles north of the Yakima County line. So that could put the 1979 jaeger sighting barely into Yakima County, if it was on the Yakima side of the river. There, the Grant/Yakima county line is mid-river. If the bird was observed from the Yakima side, on the Yakima Training Center, then it was in Yakima County. If it was observed & identified on the Grant County side, and then it flew to the Yakima side, then it would count as a Yakima County observation. If it was observed on the Grant County side & not observed flying to the other side, then it isn't countable in Yakima County. The distance from the Grant County shore to the Yakima County line there is about 0.3 miles, or 500+ yards. An identification might be made at that distance.

Doubtful, unethical identifications:
Downstream, closer to the dam, the distance across the lake is about 1.75 miles, and the distance from the water's edge on the Grant County side, to the Yakima County line is 0.9 miles. One would likely bird from a bit further back, up the slope, for a better view. I don't think an honestly accurate identification of many birds other than Bald Eagles, Canada Geese, & American White Pelicans is likely. The current Yakima County "top" eBird lister, Scott Downes, has made several of his recent reports of sightings of hard-to-find birds seem as if he made them from the Grant County side just north of Goose Island near the dam. If they'd actually been from there, he would have had to accurately & positively identify the Clark's Grebe, immature Sabine's Gull, and Common Tern from over .9 miles distance. Unlikely. But it turns out that he writes in emails that he knowingly & repeatedly trespassed on the dam to get his reported sightings, and from who knows what distance -- this despite being kicked off the dam.

By ABA rules, trespass makes a sighting not "countable"
http://www.aba.org/about/ethics.html
http://www.thebirdist.com/2013/06/is-this-bird-aba-countable.html