“Great Tit Bird Eggs Found Nearly Sterile Before Hatching, Except for One Type of Vertically Transferred Bacteria”

https://pubmed.ncbi.nlm.nih.gov/38115624

This study found that the eggs of a passerine bird, the great tit, are nearly sterile and are not significantly colonized by bacteria before hatching, with the exception of one type of bacteria that may be vertically transferred from the mother.