The grackles and starlings have been enjoying the ficus trees for years. But about three years ago, after the canopies were fully matured, the birds apparently told all their friends that Mill's the place to be, because that's about when Tempe's arborist, Steve Amelotte, noticed the area had been hugely invaded.
On-street parking and more outdoor dining patios added since 2002 exacerbated the problem. To continue the air-assault theme, it could be said that all those extra birds flocking to Mill found a target-rich environment.
The birds use the trees as sleeping quarters at night and for rest stops during the day. All the while, their digestive systems drizzle poop on the hapless humans and infrastructure below.
But they aren't fouling their nests, which are dispersed through the Valley, says ASU grackle expert, ecologist, and assistant professor Kevin McGraw. Sleeping at nest sites draws too much attention from predators. Another facet of their survival wisdom, McGraw says, is roosting together in large numbers near electric lights: They're more likely to see approaching predators and less likely to be eaten by larger birds.
Grackles are aggressive.
"If you put out seeds," McGraw says, "grackles will sift through the seeds to find what they want and chase other birds away."
Grackles aren't easily put out, or snookered.
With a budget of only a few hundred dollars, Amelotte and his crews tried thinning the ficus branches, but they couldn't thin them enough. If branches are thick enough for shade, there's enough wood for the small feet of the resting birds. Amelotte tried playing amplified recordings of distressed birds, but the real birds weren't fooled. He tried coating the branches with slippery foam, but it dried quickly and the birds paid it no attention.
"A grackle's an amazing bird!" Amelotte says, begrudgingly. "That bird does what it wants to do exactly when it wants to."
Amelotte says he consulted with a Chandler man who runs a business called The Pigeon Guy. Oddly, Tempe officials and the city's business association, the DTC, never bothered to call ASU in the past three years to find out whether anyone could help.
McGraw, who works in a lab in the Life Sciences building on ASU's main campus, is an expert on both grackles and bird removal.
But he's unsure what should be done about the grackles.
Oh, he knows how to get rid of the birds. But the solution's drastic and controversial — he wants no part of it.
Basically, he says, you'd have to keep all humans off Mill Avenue for a couple of days, during which time you'd send teams carrying net cannons to catch thousands of birds. The grackles would then be released beyond their typical homing range so they wouldn't find their way back. Even then, McGraw says, it's possible the grackle population on Mill would build up again over time, requiring another relocation a few years later.
Not only that, but the non-native starlings couldn't simply be reintroduced elsewhere, per federal regulations. They'd have to be killed.
"That's not something I'd feel comfortable doing," he says.
It's also not something the Valley's many animal-rights advocates would stand for. A few other bird-control options have yet to be attempted, and aren't likely to be effective. One mentioned by McGraw is spinning, ultraviolet reflectors that look like cheap wind chimes. Possibly, the reflectors would stress out the birds enough to make them leave.
Lasers (strong enough to bother, but not blind, the birds) could be aimed into the trees. In the Dallas-Fort Worth area, which has seen an invasion of grackles in parks and downtown areas, a DTC-like group hired a company that uses a hawk to hunt and kill grackles. In theory, the presence of the hawk (after a couple of days) scares the grackles enough to make them find other homes. So far, the brave blackbirds haven't backed down, says George Kruzick, a Fort Worth parks supervisor.
Propane cannons have proved an effective, albeit temporary, deterrent. Cannons, mounted on trucks that drive by infested trees, automatically blast sound and heat every minute or two at the birds. A few days of the blasts force the grackles to skedaddle for a week or more before determining it's safe to return. But there's a downside to this method: "It does disturb people," Kruzick says. "No doubt about it."
Because of the noise, officials have decided not to use cannons in downtown areas or places where tourists gather. Noise-wise, the solution is worse than the problem.
That's why cannons probably won't be used on Mill, says Pam Goronkin, the DTC's executive director. But she's definitely on the lookout for some kind of fix.
At the end of the summer, before the birds come back in force by October, the DTC will pay landscapers to trim the ficus branches even more. That will reduce some of the shade, but it should lessen the number of birds and, thus, slow the build-up of feces.