How High?

I've seen hawks pluck doves right off the ground. Ive never had my run "un protected" to big of a chance for me.
When i let my birds free range they seem to have an eye towards the sky. Ive seen them freeze in there tracks and also take off running for the covered run when a hawk is in the area.

thank him for the advice but do what you think is best

 

I believe the thing you want to think about with a run only being 3 feet high (AND COVERED) is that you'll have to get in there at some point in time to clean or grab a chick. Do you want to stoop that low for all that time?

 

If I were you and was going to make it 3ft. I would somehow make either a removable roof(whether a solid panel or wire mesh) or light enough to move the whole run for servicing. Mine is 6ft and covered with heavy duty snow fencing and have not had any problems and looks cool in fall when the pine needles fall on it and point looks like a grotto. I definitely prefer 6ft cuts down on work with easy accessibility.

 

At our place we have working chickens. There job is to take an area given to them and eat and remove all the vegetation. They take there job very serious and to it with gusto. Since these chicken are never in one spot for more than a couple of weeks, depending on the time of year, these runs and coop must be movable. The runs are 2' high and the coop is 4.5' high. The length of the runs vary depending on how big of an area they need to clean. The runs are modular, very light and easy to move. There just not very pretty.
https://www.backyardchickens.com/gallery/image/view/id/4967734/album/6169273

 

I'll have to agree with keeping it tall enough to get into. If it was only a couple feet wide, I can see keeping it low if you were to put a hinged roof on top so you can access the run. Keeping it taller definitely makes cleaning easier as well as enables you to access a sick/injured bird without injuring/frustrating yourself.