Subject: Why do birds congregate on lampposts and power lines at highway exit ramps

I've been observing this phenomenon for several years. Though there may be 
plenty of power lines and lampposts along a highway, birds will tend to 
congregate much more frequently on lines and posts at exit ramps or at traffic 
circles where traffic slows down. Is this something to do with air currents? 
Thanks!

Re: Why do birds congregate on lampposts and power lines at highway exit ramps