Yeah, I've had crows take dead critters ...heck live critters from me before. Never a grackle. The mystery is still on, somewhat, however.
In my increased vigilance, I noticed a tabby a couple yards over. Pregnant. She sort of sauntered toward our yard and then dropped out of sight. I just sat and watched. Sure, enough, she found a way under the fence and made it into the yard. And she made a beeline to where the missing bird was hit. Maybe she smelled blood, or maybe she remembered the spot where she took the nice bloody bird, but no matter what, she's a prime suspect.
I did take two more today. Both were male, and one at 22 yrds, just bounced and flopped. The other, I aimed for his head at 12 yds. I was thinking I was right on, though I may have hit him a bit low. But up he went, fluttered about 10 feet straight up above the fence, then flew straight into the side of my neighbor's house. Splat! Big red spot, and then more down the side of the house. I must have hit him in the neck but missed his spine. What a mess. So, I called the neighbor and let him know and met him at his fence. Rather than let me hop over and clean it up he was laughing and took care of bird and blood himself.
Nice neighbor.
So, that's 6 sparrows in one day and there are more. I'm on the war path. I no longer care if the parents of the brood in the building next door die. There are too many of those guys and I'm just now starting to get song sparrows, white-crowned sparrows, and downey woodpeckers coming in regularly. I'm not going to jeopardize that by letting the hosps get a breeding actively again. They must be aggressively controlled.
"House Sparrows may raise 2-5 (average of 3) clutches of 3-7 chicks each breeding season, (averaging 20 chicks per season) which fledge in 14-16 days. They start claiming nestboxes early in the season (February and March). Since they are relatively long lived (up to 13 years), one pair can at potentially quintuple the population in one year. "If unchecked, a breeding pair can grow to over 2,000 birds in two to three years." (Bird Barrier America, Inc.) (Using some conservative assumptions, I calculated one pair could theoretically increase to 1,250 birds in 5 years.)"
http://www.sialis.org/hosp.htm M