Nothing will happen. There is no path through the bird on a wire. I have three phase 7200 volt lines on my residential street, another set much, much higher but here nor there. Birds sit on the lines all the time. The 7200 volt phases alternately drive transformers to feed the residences. Each transformer presents a "load" and each transformer has a 7200 volt primary. With or without loads the bird on a wire will be just fine as there is no path for current to flow through any of the birds. The video I linked to using a helicopter for high voltage line maintenance makes all of that pretty clear. The bird on a wire will do just fine whether that wire has a load on it or not.Let's see the end of the wire that the bird is sitting on is connected to one side of the primary coil and the other side the coil is either connected to another high voltage second phase or to the ground. ( current has to be there to charge the primary coil of the transformer).
If you cut that high voltage wire and connect a load on it, if it doesn't fry it, (very high voltage low current), what would happen? And would you measure a potential difference across that load?
My suggestion, based on the very first post, would be a career in another engineering discipline. While a good number of years have passed my recollection of AC theory came in around the second semester which is where most students who were going to change majors did so. Mechanical engineering and structural engineering are nice and there is always architecture.
Ron

