My favourite blue tit fact is that they are sexually dichromatic under UV light only. The male crown is brighter in UV and females prefer males with brighter crowns. Mere humans can't tell the difference.
Comes from this rather brilliantly titled paper: Blue tits are ultraviolet tits https://pmc.ncbi.nlm.nih.gov/articles/PMC1688906/
Read this as "Male humans can't tell the difference." and found it comic
They UV will sharpen them up and get them ready for a bit of the old Ultraviolets.
> Comes from this rather brilliantly titled paper: Blue tits are ultraviolet tits https://pmc.ncbi.nlm.nih.gov/articles/PMC1688906/
Made my day. Love it when you can tell they could have titled it something else but decided the joke was technically accurate and worth it.