Don't know what my chickens are eating

[chick_magnet]

I can't see what my chickens are eating. At first when they were eating the from the grass i didn't think too much of it but now they are eating at concrete surface and i can't see what they are eating. What could they possibly eat that is so small. This is just me being curios this is my first flock of chickens. Also beside bugs what could they eat from the grass?

 

[Tracydr]

About six of mine kept going over by the fan to dig, scratch and peck this afternoon. I tend to dump their waterer near there but when I looked to see what kind of bugs they were eating I couldn't see a thing. I started to wonder if they just wanted to stand in front of the fan and dig damp dirt, pretending to eat and staying cool at the same time?