Assessing the age of chicks

[iPringle]

We bought eight chicks last Saturday from Tractor Supply. Four black Australorps and 4 New Hampshire's. I didn't think to ask about the age of the chicks when I bought them, and now I'm reading about different stages in their development and when to do what with them and I'm realizing I wish I knew how old they were when I purchased them.

This is a picture of them the day we bought them, so now they've been with us almost a week. Any idea how old the chicks are from Tractor Supply? Or how old they are from this picture? Or even a handy chart to assess age based on size?




We have them on some organic feed we bought from Purina, but once that runs low I want to switch them to my own home grain feed mix and I need to know their approximate age in order to get the protein levels correct.

 

[azygous]

A photo outside the brooder away from the red light and closeup of rumps and wings will give us a better shot at telling you their age. That photo doesn't show these necessary details.

 

[aart]

They look to be around a week from wing feathers.
Farm store birds are usually 2-3 days old to maybe a week.
I wouldn't sweat it too much, a few days won't matter.