Oh really? Maybe you ought to do a little more research.
Pssst... The blades of a fast turning turbine are practically invisible and remember, we're dealing with bird brains.
Yes, really.
They're not "fixed highways," whatever you want to call them. The birds will fly around.
Indeed, there are hundreds of these windmills in Big Spring, Texas. Heard the same B.S. about killing migratory birds and invisible blades.
Have yet to see mass killoffs of the birds going South.
I have seen birds fly over, under, and around them, though.
In fact, your link calls them a "theoretical construct":
The terms "migration route" and "flyway" are to some extent theoretical concepts, while the latter has, in addition, come to have an administrative meaning. Migration routes may be defined as the lanes of individual travel from any particular breeding ground to the winter quarters of the birds that use them. Flyways, on the other hand, may well be conceived as those broader areas in which related migration routes are associated or blended in a definite geographic region. They are wide arterial highways to which the routes are tributary.
I believe the "flyway" in question (the Mississipi Flyway) stretches from New Mexico to the Mississipi River or so.
Indeed, there are a total of 4 flyways in the united states, each roughly corresponding to a TIME ZONE.
"Flyway" does not equal "Highway" in other words. "Migratory route" (the narrower term) doesn't, either.
If this was smack in the middle of a well-defined migratory route, there might be an issue.