On last month’s expedition to ring a brood of Barn Owls we found another barn containing a nest-box that no-one had been aware of. Closer inspection revealed three newly-hatched chicks. As they were reckoned to be about one, three and five days old, they were too young to be ringed that day.
We came back nearly six weeks later and found an adult (which immediately slipped away) and two well-grown chicks. Don’t ask what had happened to the third…
These chicks were slightly less advanced than the other brood when we ringed them – see how much down they still have compared to these.
M. who was supervising (Barn Owl ringing needs a Schedule 1 endorsement to the ringing permit) looked up the wing measurements in the tables, and pronounced the birds to be between 44 and 46 days old. This agrees very well the estimate of one to five days old when we first found the brood. It also suggests, unsurprisingly, that it was the youngest sibling that did not survive.