Well Dirtgirl, I just couldn't stand seeing your post not get answered anymore! I didn't respond earlier, because I've never seen foil in my carolina wrens' nests. It's very interesting though! Those birds find the strangest/funniest places to build their nests! One year, we had our table saw on our big, covered front porch, with a tarp over it (yes, we're pretty fancy here), and those little guys built a nest right under the tarp! Fortunately, we didn't need to use the saw for awhile. I have tarps for an awning in front of my chicken coop, that I keep drawn up in summer, and pulled down in winter, to keep the wind out. Well, there's a nest inside that drawn-up tarp now. In the winter they sleep on a ledge right outside the chicken coop. As part of my nightly ritual in the winter, of closing up the chickens, I shine my flashlight up there, and make sure there's several pairs of feet. They are cute little guys!

WBNU is the abbreviation for the white breasted nuthatch, so I assume it'd be BHNU for brown-headed nuthatch. TUTIs are wonderful tenants and parents. Last year I had a pair in a bluebird box where the brood was almost wiped out by HOWR (house wrens). There were 6 eggs and the day before they would have hatched, I found all of the eggs on the ground below the nest box pecked to varying degrees. I put the least damaged egg back in and it hatched. I had a nest box camera and saw that the female nuthatch RARELY left the chick alone and stayed with it every night of its life. I don't know if that's normal or it was this female's reaction to having only one chick. In any case, they are a delight. Hope you have a nest of them someday. Bluebird blessings, Linda...

If the young have already fledged, the eggs left behind are infertile. If she couldn't hatch them, they are not viable eggs. Since you said the young have left the nest, you can throw out the nest and the eggs.

They don't always build their nests in the best places. I had a Carolina wren build a nest in an orchid pot and the weather suddenly became extremely hot. I had to move the orchid into the shade. Either this scared her off or she'd already seen her "mistake" and moved on because no eggs appeared. I agree you shouldn't interfere. If she built the nest in a bad place, well, it's called survival of the fittest. But they'll probably be fine. Babies' mouths are usually wide open.