Treated lumber that you buy today does NOT contain arsenic. (Older stuff you bought a few yrs ago and still have lying around, *that* does). Even the older arsenic-treated lumber, it is not clear how much arsenic contamination of soils it actually causes under normal sensible use conditions, and the dilution factor in your birds' diet is so inconceivably vast that I totally would not worry about it.
And, again, if you buy NEW treated lumber, arsenic is not an issue anyhow.
If you don't use treated lumber use cedar or redwood (or locust or osage orange if you have access to them, which hardly anyone does) -- don't use t-posts unless you are ok with having a fairly flimsy fence and will never have any desire to put a good strong roof on it. While t-posts themselves are fairly strong, they are not very resistant to being pushed over and for a variety of reasons it is quite difficult to use them to support higher-up elements such as supports for a wire 'roof'. Also t-posts do not make strong corner posts.
Good luck, have fun,
Pat
And, again, if you buy NEW treated lumber, arsenic is not an issue anyhow.
If you don't use treated lumber use cedar or redwood (or locust or osage orange if you have access to them, which hardly anyone does) -- don't use t-posts unless you are ok with having a fairly flimsy fence and will never have any desire to put a good strong roof on it. While t-posts themselves are fairly strong, they are not very resistant to being pushed over and for a variety of reasons it is quite difficult to use them to support higher-up elements such as supports for a wire 'roof'. Also t-posts do not make strong corner posts.
Good luck, have fun,
Pat
