What are those weird Black birds??

As we walked down town in Austin there were these flocks of black birds all around making the most weird sounds.They were not unpleasant sounds, but still they made us stop and stare. Andy thought it might be a squirrel as we do have squeaky squirrels that trill like these birds back in India. But I was sure they were sounds coming from the birds.

There were a more buiscuit coloured variety as well and I think they are females. Take a look--

Their droppings were all over the pavements, splattered across the old brick roads and under the avenue trees along with the rock pigeons. Apparently they are called Great Tailed Grackles and they have becom a sort of invasive pest across the state of Texas. Very interesting for me a Science and Environment journalist -- great story idea.