Bizarre bird behavior

My double-take was so strong, it almost gave me whiplash.

At first glance, it looked like a very normal scene: a sunny Saturday morning in Clear Lake Shores, a handful of feral Muscovy ducks lounging by the waterside. 

But waitaminute - let's zoom in on that...

Notice anything a bit odd?

How about now?

Those two with the grey heads were apparently only thinking they were Muscovy ducks.  They were actually black vultures. 

Getting ready for flight.
Unfortunately, all I had with me was my crappy camera phone, which does not do well while zooming in direct sunlight.  I have never been this close to a "wild" vulture before (or at least, one who should have been acting wild), and here was the experience for me, in a gravel parking lot in Clear Lake Shores.  Who'da thunk. 

I have never seen vultures intentionally flocking with Muscovies before, but apparently this type of behavior has been reported in greater Houston previously, at least to a limited extent. 

It's no secret that suburbanization has assisted certain wild species.  Just yesterday, GCDN published a short piece describing the three thriving coyote dens that are located pretty much in the heart of Galveston.  We all know from visual experience that both black vultures and their larger cousins turkey vultures thrive on road kill. 

Seen daily above a freeway near you.
Screengrabbed from this site.

But wider social integration??  Inter-species??  What is the basis for this association?  Do the vultures perceive of themselves as being indistinguishable from Muscovies?  They are basically the same size and of similar gross appearance, but it's not typical vulture behavior to lay down and chill out in the middle of human activity - in a grassy swale at the edge of a commercial parking lot which had just received about fifteen cars filing into it for the opening of the Farmers Market.  That type of nonchalant hanging out is typical Muscovy behavior, however. 

Nature's great mysteries, unfolding in a suburb near you.