Among most photographers, conventional wisdom says: “Do not shoot in direct sunlight – it is unflattering”. A small number of bird photographers, on the other hand, insist that bright sunlight striking the front of your subject is exactly what you want.
My own experience is mixed. With some birds (like my favourite Red-Winged Blackbirds and Cardinals), bright sunlight leads to an unpleasant combination of dull and over-saturated colours; you need softer light, like you get on a cloudy day, to bring out the subtlety hidden in their apparently straightforward colours. With some birds, however, photographing them in soft light means you never see the true brilliance of their feathers. Grackles fall into this second category.
In shadow, or on overcast days, Bronzed Grackles are very dull-looking birds: sort-of dark brown with sort-of black-ish heads. In full sun, however, they are iridescent bronze shimmering with purple, with deep blue-green heads. To only take a photograph in soft light is to never see their true beauty.
(Incidentally, they’re called Grackles because they say “grackle grackle”! http://www.allaboutbirds.org/guide/Common_Grackle/sounds )