Do we yield to the birds or the other way around?

I was driving down Crowchild Trail this morning in moderate traffic and saw something I don't recall ever seeing before. A bird (it was too far away to determine the variety - but it was almost as big as a hawk) was flying in formation with the cars. At first I thought it was just a coincidence, but this bird stayed with the flow of traffic for a good several hundred metres, right behind a van, then deked off to the left into a residential area.

Weird.