Hello there, I am currently stuck with a young Great Tailed Grackle. I'm finding him to be very engaging and the level of intelligence is quite remarkable. "Cackle" as I ended up calling him was found by my husband while mowing the pastures with the tractor. He almost ran over the bird. "Cackle" was an acre away from the nearest nesting site, he was extremely underweight, should not have been out of the nest and had the "weaving and unsteadiness" I've seen in young birds that are beginning to develop rickets.
Feeding him is easy enough, before an evil possum beheaded my hand raised group (yes they even ate from my hand) of Guinea Fowl, I had a baby bird mix used for them. It's amazingly easy to prepare for a young bird. Hot water to the right consistency, usually a heavy'ish paste that you can roll worm shapes with does well. In Cackle's case during the first three days, his symptoms worsened. I do have gel caps containing easy to metabolize calcium. I started adding the calcium to Cackle's mix and the weaving and unsteadiness disappeared within 48 hours. The bird mix I'm using is a high protein, high calcium and everything else a fast growing baby bird needs to do well.
(My Starling, "Birdie Num Num" did very well on it along with a number of rescued and released Red Shouldered Blackbirds and Vesper Sparrows)
Living in the country as I do, feed stores make it easy to get large supplies of premixed just made for babies bird pellets used for raising Guinea Fowl, Pheasants and all sorts of birds that are omnivorous like Grackles are. Great Tailed Grackle males grow extremely fast and develop feathers faster than any baby bird I've seen so watching him over the last three weeks has been interesting. An unwell bird will be tipped out of the nest and driven off. It's the first time I've had to add calcium to what I've used to raise baby birds.
Contact is necessary, talking to them is important. Grackles are talkative birds and tend only to be cuddly while very small. They assert their independence later. "Cackle" would be going on plumage, approximately 20 days old and at a point where he is ready to fledge. Great Tailed Grackles will continue to follow their mothers around for some time afterwards to learn how to forage. Some might ask how I know it's a boy and how on earth would I know what kind of Grackle he is.... Well, strangely enough considering where we are in northern central Illinois, our small farm hosts a large Great Tailed Grackle nesting colony. The variation of Common Grackle we have are "Purple Grackles" - their bodies are solid black in the males with mainly a purplish or blue and purplish sheen to the feathers. Great Tailed Grackles are not born with brown eyes most of the time, they are a curious silvery blue'ish color and in Cackle's case are turning distinctive yellow. He has absolutely no brown or even mildly brownish feathers anywhere. The Great Tails are more musical than most, not much in the way of "screeching" here, they sing, they're highly social and tend to feed along with the Red Shouldered Blackbirds and Starlings. They even get along with the Ravens. Common Grackles are not something I see much of, I saw ONE solitary male for the first time this year yesterday as he was hanging around the kitchen window until the Cardinal's ran him off.
Well raised Grackles are fun, when released, even if they migrate they usually come back to where they were found and will come back to the people that raised them. Our farm is a haven for them as since we are surrounded by corn growers, anywhere else they get trapped, poisoned or shot.
Developmentally, I've noticed some extremely interesting aspects of behavior. I'm not originally from the USA, I did do a lot of rehabilitation and rescue however in Australia so if I find a new bird, I do a lot of reading to find out what I end up with. In the time Cackle has been with me, his growth rate has been astounding. He's tripled his weight. As an underweight and underfeathered baby with these crazy eyebrow tufts and tufts in his wings, he was around the same size and weight as my adult Starling. After making sure there were no parasites, I have allowed some interaction between them. Cackle at least knows about other birds. He's just starting to get the idea of flying, so I'm now leaving his cage open during the day. Despite his curiousity, after watching a lot of footage of wild Great Tailed Grackle behavior, I've seen that they follow their mothers around for quite some time going on the length of tail that the fledgelings develop while still doing the gaping and squarking saying "FEED ME". I've observed this in the colony that nests here every year. One of the males I talk to is funny, he meows like the barn cat.
Every year there is always several baby birds picked up, raised and released. My starling was declared unfit for release though he should have been too young to imprint. His parents and siblings were "Catted to death", going on the injuries, he fell from the barn loft as one leg was broken, one leg was mildly dislocated. He was found first trying to desperately beg food from my then 8 month old filly, and then crawled to my husband who brought him in and said "Can you save it?" I did, the little idgit has healed well, one foot will never work properly, he has trouble gripping with it. At a year old he's developed quite a vocabulary along with a huge range of birdsong he's imitated as he's by one of the kitchen windows for sun exposure during the day, a good view and able to see a large variety of other birds.
Personally though, I LIKE Grackles. They keep down a lot of pests around our farm that I don't like including the nasty little crickets that used to eat the roots of the grass here. They are entertaining to watch, quite bold and fearless. I check the nesting colony regularly - most have opted for the huge level of pine trees that we have. Walking through them I'm usually trailed by boisterous males running around like fools on the ground singing at me. Knowing how aggressive they can be (The first Great Tail I met was in San Antonio and it HATED my mother in law and attacked her on sight along with cats, dogs and most other things at nesting time), I find it curious that like the other birds here, they're pretty laid back, perhaps because I feed them from time to time.
As per usual, I've been overly verbose. My usual company is Arabian horses and the birds here, some of which follow me around. I do however need to feed the extremely fast growing screechbox who is trying to convince me that he is fading away to a starving shadow.
I DO keep the state Wildlife Department updated on any birds I pick up, they don't care what I feed and prepare for release so long as it IS released. If I wasn't dealing with serious health issues, I'd be setting up as a licensed rehabber as there are none for rescue in my area. For now, I just keep those who need to know informed of what I have and progress reports. Next year, I start my training to get a falconry license. Now that I look forward to. I used to rehab raptors in Australia, I'd like to do it again.
I'm not sure what grackles eat. They're insectivores, aren't they? 
