I was idly scrolling through some old Facebook posts when I came across a post describing the additional 24 nest boxes that we installed at Edgecombe flats in 2021 where I was reminded that we painted every other chamber black inside. See here.
I had forgotten about our experiment, but in 2023 we surveyed these boxes and found 16 of them occupied. I just checked the data and found that 8 were in the painted boxes and 8 were in the unpainted ones.
This would support the hypothesis that Swifts really don't care.
The probability of getting exactly this result, if the Swifts have no preference would be 0.333
The probability of scoring 9:7 or 7:9 is, in each case, 0.237 - so being one off would be 0.474 - more likely than 8:8
This adds to a similar experiment at Trumpington Meadows in 2019 where in 10 boxes, 5 black and 5 unpainted, there were 4 pairs in the unpainted boxes and just 1 in the painted boxes
It does seem that there is little point in painting the inside of Swift boxes black.
More experiments like this would be useful corroboration.
This was a properly designed experiment. The double boxes were numbered 1 to 12 with each chamber labeled e.g. 1L or 1R. All odd-numbered double boxes were black on the left inside and all even-numbered black on the right. This should eliminate any preference that the birds may have for left or right
