Non broody hen sits on eggs after laying them

[AmmarAhmadKhan]

Hi. Two of my hens, one of them is buff cochin and other is some mix breed of black colour, they always sit on their eggs after laying for most of the day. They are not broody, and they do this everytime they lay an egg.
Can anyone tell what's the reason for this?

 

[janiedoe]

Some hens or off the almost immediately, some set for a while afterwards. Some of mine seem to do to agitate the girls who want in to lay in the favorite nest.
My broodies sometimes start out staying longer and longer in the nests before they commit
Some hide out in the nest when they are being bullied. Are they low in the pecking order? Do you have enough nesting boxes? Do they have supplemental calcium?