• Tropical Family. Also members of this family are the blackbirds, cowbirds and orioles. Common grackles are found all across the mid-west and east coast. Boat-tailed grackles live along the eastern and southern seacoasts while great-tailed grackles are found mostly in Texas and the south-west. Grackles are aggressive birds who will colonize in large numbers. These birds are very noisy, their gregarious nature is very apparent when observing their roosting and nesting sites
• The common crackle has a green/blue or purple iridescent tinted black plumage with a glossy purplish head, neck and breast with the female of the species, slightly smaller and duller colored. Boat-tailed and great-tailed grackles have very long "v" shaped tails which crease in flight, hence the name "boat-tailed". They are similar in color to the common grackle but are larger birds (16 inches long versus 12" long). Female great-tails resemble the males while female boat tails are dark brown in color Great tails differ from boat tail grackles with their bright yellow eyes and more uniform color.
• Nesting 
  Grackles build a bulky yet dense nest of twigs, grasses or weeds lined with feathers, rags or dried grass. The nest may be held in place with a foundation of mud or cow dung. Grackles will nest in a variety of places from willow swamps, dense brush to tall trees with trees being the most common. Boat tail grackle nests will seldom be seen more than twenty miles from the coast.
• Breeding 
  Grackles breed during the spring. They usually lay four to five eggs in a single brood for the year. Common grackle eggs are a pale green to light brown with purple and dark brown streaks and blotches. Boat tailed grackles have lighter blue to grayish eggs with dark streaks and blotches. The eggs take 14 days to incubate with the young being able to fly about three weeks later. 
• Cycles 
  Grackles have a definitive seasonal behavior. They nest and breed as one pair or in small groups in the spring time. In the fall, the birds will fall to form large colonies with the juveniles first forming the groups and later joined by the adults. These large colonies can number in the thousands. In colder, northern climates the flock will migrate south, while southern birds will stay put or move into a more urban location. These flocks will usually take over several trees or urban dwellings for their evening roosting. In the winter, their feeding site may be quite far from their roosting spot, making trapping or baiting difficult.

   

 ( Courtesy of Bird Barrier)