Breeding swifts?

Working in the garden today and I was surprised by two swifts flying low behind the house and one entered an old starling box on the outhouse….
I’ve been trying to attract swifts (tårnseiler) for years to the house and have one swift box higher on the main house, but they chose this instead!
In the video you can hear the bird “screaming” quietly and another sound….could this be chicks?..strange I haven’t noticed this before, but I’ve been away a lot and I have seen two birds flying low in the same area a couple of times this summer (latest last weekend) and also last summer on several occasions (presumably prospecting). After the one bird left I could hear noises in the nest (I didn’t see both birds enter the box)

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