Noises in the wall, newly purchased, built in 2016

The construction company only recently closed this slit at the edge of the house at our request. Additionally, there were similar ones at other points on the roof. The whole thing was regarded as a "cosmetic defect",

I wonder what one must have been smoking to call such a huge hole a "slit". A slit is at most what you can see in photo 6020 – which is, however, only between the fascia board and the adjacent plaster. Behind that lies – apparently on both sides of a rafter overhang – a cavity roughly estimated to be the size of a foal’s leg. Whoever sealed this supposed slit probably owes it to the winter dormancy of the inhabitants living behind not being stung. Even though I would consider the carcass on the window sill to be an insect, it most likely suggests a wasp nest. Now in spring it already gets warm enough several times a day for life to stir there again, presumably feverishly working on an opening to the outside world. Consult a pest controller or the fire department; neither praying and waiting nor doing it yourself is appropriate here. "Cosmetic defect" only applies in the sense that the base plate is probably not damaged – I suspect a hollowing out of the insulation between the rafters to the mentioned extent.

Huh? Not 5 years according to the Building Code?

Would you like to answer that as well?

Would you like to answer that too?

Of course, very gladly.
I just asked my husband again. The house was apparently built in E/2016. The warranty therefore only starts in 2021. I must have confused "next month" with "next year". Phew....

We have now contacted an exterminator. Meanwhile, the noise sounds like small wing beats,... also in the next room. If it stays like this for another week, he will probably come by and possibly drill into the wall.

If it stays like this for another week, he will probably come over and possibly drill into the wall.

Are you and/or the pest control officer of madness fat prey?
If so, may he do this with fire department and emergency doctor on standby!
Very likely no swifts are nesting there, but wasps, bumblebees, or hornets – in a nest behind the supposed little slit the size of a deer's stomach. And these are not loners – if they are pleased with a small drill hole, then a whole colony is pleased. One should have the syringe with the antiserum ready by then. I would first clarify what awaits you there using sono- or thermographic methods.

Are you and/or the exterminator of madness fat prey?
If so, may he do this with the fire department and paramedics on standby!
It is very likely not swifts nesting there, but wasps, bumblebees, or hornets – and in a nest the size of a deer stomach behind the supposed little slit. And these are not solitary creatures – if they are happy about a little drill hole, then a whole colony is happy. One should have the syringe with the antiserum already prepared. I would first clarify what awaits you there with sono- or thermographic methods.

Unfortunately, I have absolutely no knowledge about this here and simply trusted what the exterminator suggested..... Does this sono-thermographic method normally come standard with exterminators or whom should I turn to here?