The owl files – Chapter 3: Why I am worried!

21 June 2022

Why I am worried!

Yesterday evening I waited for the female to leave the nest for her customary stretch break and then popped up the ladder to check the nest contents .   .   . and there were two eggs. The second egg was laid around 4 days after the first – and this could be a problem later when the eggs hatch!

In owls, the female begins incubation with the laying of the first egg – so in this case the first embryo will be 4 days further along in its development when the second egg was laid. This could mean that the first chick hatches out around 4 days ahead of the second – and as the chicks usually double in size every 3 days; the older chick will possibly dominate whatever food is brought to the nest.

Normally, eggs are laid (and hatch) at roughly 24 hour intervals, and although there is a difference in the size of the chicks in the nest, this is not usually not significant.

Cainism – where the older chick harasses, or even kills its younger sibling(s) doesn’t happen in Spotted Eagle-Owls but if the size difference between chicks is too great, the smaller (younger) chicks may simply be out-competed for whatever food is in the nest.

By Geoff Lockwood