The Brewers initially believed their unpaid visitor was a peregrine falcon. Many MLB.com readers correctly identified it as a hawk but debated the variety. Cooper's? Red-tailed? Goshawk?
"It's a Cooper's hawk, and I'll tell you why," Parr said. "A goshawk has a pale line above its eye. That's the critical thing that will fix that for you, because if you look at that bird, it has an all-dark head. The light eyebrow is always present [on a goshawk], and that bird just doesn't have it.
"So that's your solution. The goshawk lobby is, unfortunately, incorrect, but I can understand it. It's a related bird that looks very similar."
The Cooper's hawk is common in Wisconsin and actually has some recent history of getting into places a hawk should not be. In January, a female Cooper's hawk spent about a week inside the Library of Congress before she was finally captured and taken to a rehabilitation center in Virginia.
Washington Post readers, voting in an online poll, named her "Jefferson," because she spent her time in the main reading room of the library's Thomas Jefferson Building.
"They're pretty adventurous when it comes to prey," said Parr, and indeed, the Miller Park hawk was hunting an unlucky pigeon when it found itself stuck under the ballpark's closed dome. "The Cooper's hawk seems to be on the increase, and one of the theories is that they've learned to take advantage of pigeons and starlings during the winter.
"It's partially surprising on the one hand, because [a baseball stadium] is a strange place to see a Cooper's hawk. But it all kind of makes sense. He was pretty hungry, is what it comes down to."
The Miller Park hawk does not have a name but does have a Twitter feed -- @MillerParkHawk -- that drew more than 1,300 followers in 24 hours. Appropriately, he was only following one person -- Astros right fielder Hunter Pence, who warily eyed the hawk between pitches on Sunday as it rested in the outfield grass.
The Brewers have their own hawk history, Hall of Fame broadcaster Bob Uecker said Monday. He recalled that a group of 10 or more red-tailed hawks used to nest atop the light standards at County Stadium.
"They were huge birds," Uecker said. "You could sit there in the game and watch them. They were really amazing animals."
County Stadium also had its share of seagulls, which became a problem in 1993 when dozens of gulls interrupted a game against the Yankees, either disturbed by a Harley-Davidson reunion or searching for moths hatching in the grass -- or both.
The next day, the Brewers brought in Gus the Wonder Dog, an animal on loan from the Wisconsin Waterfowl Association that was trained to keep the birds away.
"I remember that," former Brewers pitcher Cal Eldred told the Milwaukee Journal Sentinel. "They had to bring in the dog to chase the birds, then they had a guy with a shovel chasing after the dog to clean up after him. That was pretty embarrassing, I'd have to say."
The hawk, though, is welcome back. Plenty of seats remained for this week's series against the Reds.