These opportunistic Great-tailed Grackles were observed as they helped themselves to some soggy pieces of bread left behind by duck feeding park patrons. In the pictures below the big black male grackles are contrasted nicely with the smaller, duller colored females.
On occasion, the males would take time off from eating strike poses that were meant to impress other, rival males. Wings down and beak straight up is certainly a stance meant to intimidate!
Here is what Wikipedia has to say about the behavior of the Great-tailed Grackle:
This bird has a large variety of raucous, cacophonous calls, some very melodic, but is considered to be a noisy pest species by some. Its range expansion has not been aided by human introduction.
The females can travel in flocks and they share food. When a male spots a female, he engages her by puffing up and gaping his mouth. He then proceeds to make loud calls and follow the female. The female will allow the large males to mate with her; she will usually reject smaller males. Before dawn and after sundown these birds often congregate in large numbers (known as annoyances) in a particular area, for example roofs and tree branches. There they sing and caw for long periods before taking wing simultaneously until the next congregation. Grackles are cunning and opportunistic birds and are a common sights in towns and hotels throughout Central America. They are omnivorous and brave, often approaching humans in search of scraps of food.