Is Chupacabras a Terror Bird?

The answer, of course, is almost certainly not, but the idea occurred to me when reading a recently posted description of a sighting in Texas:

The features we both noted were: About four to five feet tall and ran on the two hind feet. The knees bent backward, not forward as a human’s. It made it across the road in three or four seconds. It had the body of a slim small child, not like a fat kangaroo. The arms chugged back and forth like a person running. The head had a pointed chin and a pointed top at the back like a rooster’s comb. The body looked gray or some other dark color. The thing looked to be an alien to both of us. We have never seen a picture of any [conventional] animal that resembled what we saw. It seems there have been many sightings of such a thing in the past. These are found on the Internet under Chupacabras.

Many of the features described sound distinctly bird-like:

• It is bipedal.
• Its "knees" bend "backward".  (Birds' knees don't actually bend "backward"; what people mistake for knees are actually ankles.  Birds have fairly short legs but very long feet, and they run on their toes.)
• The "rooster's comb" is compared by the witness himself to an avian feature. 
• The "sharp chin" sounds compatible with a beak. 

It so happens that there was a giant, flightless bird in Texas a few million years ago.  Titanis walleri was a so-called terror bird, the only one known to have migrated up from South America when a land bridge finally formed between the two continents; fossils of it have been found both in Texas and in Florida.  Furthermore, it does not seem to have been able to have folded its wings back in the same way most other birds do; perhaps the motion of the wings as it ran would have looked like "arms chugg[ing] back and forth like a person running."  

However, if there were a breeding population able to sustain the species through the many millenia since their last known fossil, it should have been seen much more often.  If Bigfoot is unlikely, a surviving terror bird is even more unlikely.  This is more a topic for fiction than an hypothesis for serious science. 

In fact, a Google search shows that the idea that the "Chupacabras" might be a terror bird had already occurred to others, and in fact there is a novel (The Flock, by James Robert Smith) about terror birds surviving in central Florida.  As animatronics at Epcot Center, maybe; otherwise, I'm afraid not.

So what did these people see in Texas?  My guess is some other large bird.  Maybe it was wounded, or maybe they so little expected to see a large bird that their brains tried to find other categories for what they glimpsed -- and remember, all they got was a glimpse.  I'd be inclined to guess a sandhill crane, but it's hard to imagine its long beak being mistaken for anything other than a beak.