here's some information from "Avian Medicine: Principles and Application- Abridged Edition" by Ritchie, Harrison and Harrison.
Excessive comsumption of salt can lead to:
polydipsia: excessive or abnormal thirst
polyuria: excessive passage of urine
depression
neurologic excitement
tremors
opisthotonos: severe spasm in which the back arches and the head bends back and heels flex toward the back
ataxia: loss of coordination
death
On the other hand, a deficit of sodium can also cause problems:
In some parrots, sodium deificiency may play a role in some cases of self mutilation. It can also lead to:
"a decrease in cardiac output",
hemoconcentration: fluid is removed from the blood resulting in a higher concentration of red blood cells- thicker blood
reduced utilization of protein and carbohydrates
soft bones
corneal keratinization: keratin (the protein that makes up hair, skin, and nails) is deposited in the cornea
gonadal inactivity
adrenal hypertrophy