55 to 60 degrees is about the right range, although some butterflies common to mountainous or alpine regions fly in colder temps. Rather than temperature solely determining flight, each butterfly species has a time period of usually weeks that it is on the wing, there is time overlap between species and it varies by region. Butterflies that have multiple broods (generations) per year (includes whites and yellows) will be seen over a wider time period than single-brood species.

I hope the mouse hadn't eaten any poison. But......maybe the mouse filled the jay up so much, it was too full for peanuts? Hopefully, it will be back.

OK, I get it now. Real chimney to a woodburning fireplace in the basement. So the chimney has to stay. (I was thinking perhaps it was a water heater or furnace flue and could either be re-routed or decommissioned if newer heating unit has been installed.) Probably masonry but possibly prefab insulated chimney pipe. But the electric fireplace add-on is going to be demolished so you're reclaiming some floor space and are opening up part of that wall. So we're left we how to contend with what's left, which is exactly what you said from the get-go. I was over-thinking it. OP not in possession of the house until August so can't go poking & peeling off layers of stuff. Another couple of ideas after seeing some pictures. First one won't work for you but will toss it out as an idea that might work for someone else. After the fake fireplace is gone, frame it out wider and hang the TV there, with storage accessed from the side. Second idea is a tweak on the first one. Frame it out wider and make the whole shebang look like a cabinet. Part of the 'cabinet' would be chimney but the other half would be real storage. Put doors/ drawer fronts on all of it with only half serving a real purpose. Either stash sofa throws/ DVD's etc. there or turn it into pantry. (The pantry could open up to the kitchen side with dummy doors on the living room side.)

Anytime you have pollinators running about... I would avoid the sprays too.... too much collateral damage. So I've had a few dutchman's pipe vines on my pergola for 10 years... and haven't see the Pipe Vine Swallow Tails before until my wife caught a "butterfly that was flying around the vines all day" at work. So I collected a leaf with eggs on in to raise inside... and now we have 34 of these guys going to town. Very fun to watch. There survival rate outside must be minute... out of the 15 plus egg clusters outside... i find one batch of caterpillars left. The rest are gone.https://www.flickr.com/photos/152429063@N05/shares/576i9J