Loading small cardboard boxes into her van on Wacker Drive in downtown Chicago, Annette Prince pauses to show what's inside one of them -- a tiny songbird that died hours earlier.
The yellow and black warbler had flown thousands of miles from Central America when it struck a building in the Loop.
"He avoided all sorts of trouble and weather and starvation, and then he hit a window," Prince said. "It just seems tragic that he almost made it to his breeding grounds. He was probably going up to Wisconsin or Canada where he would nest."
For Prince and other volunteers with the Chicago Bird Collision Monitors, the goal is to prevent as many migratory birds as possible from sharing the warbler's fate.
So each morning during the spring and fall migration seasons, teams of collision monitors comb the streets of downtown Chicago searching for birds that have been traumatized after crashing into windows.
Surviving birds are rescued by the volunteers, placed into paper bags for protection and then taken to Willowbrook Wildlife Center, a DuPage County Forest Preserve District animal rehabilitation facility in Glen Ellyn.
Willowbrook has been assisting the Chicago Bird Collision Monitors since the bird conservation project started in 2003.
"They love what we do, and we love that they are helping these birds," Prince said. "We could not do as much if we didn't have the support of Willowbrook."
The project, which is affiliated with the Chicago Audubon Society, sends nearly 3,000 birds a year to Willowbrook for evaluation and treatment, forest preserve officials said. They include more than 170 different species of birds, from loons and owls to hummingbirds and warblers.
More than 2,000 of the injured birds come from downtown Chicago, a natural magnet because of its abundance of tall, lighted buildings. The remainder come from areas throughout the Chicago region.
"We've had some days where I've driven 200 birds out of the city," said Sandy Fejt, site manager at Willowbrook. "It just breaks my heart."
On the positive side, most of the collision-injured birds can recover if they're saved from the perils of city sidewalks and streets.
"Had those volunteers not picked them up, the birds most likely would have been eaten by a gull or a crow or a rat ... or trampled by the commuters coming through," Fejt said.
Prince said the effort to save such birds is necessary because the animals are critical in maintaining a healthy environment.
"They are very important to controlling the balance of insects and pollinating plants and distributing seeds," she said, adding that some bird species have declining populations.
Humans have something to do with that; they created the new obstacles along the routes the migratory birds have been using for thousands of years.
"They had learned to adapt to all sorts of hazards," Prince said. "But buildings and lights are this new thing in their world that they don't understand."
Birds living in the city usually don't strike windows because they're accustomed to an urban environment, but the same can't be said for birds from Central and South America.
After flying at night, those birds look for a place to land during the early morning hours so they can rest for the day and feed. If they're flying over a big city, they can be attracted to the lights. Some try to fly toward trees inside a building lobby not realizing that transparent glass is in the way.
"They're tourists to the city," Prince said. "And we feel like we owe them safer passage."
One morning earlier this month, about 16 volunteers covered a square mile of downtown Chicago. More than 20 migratory birds were rescued that morning. They also collected about the same number of dead birds, which are sent to Chicago's Field Museum for research.
As for the collision-injured birds that survive, they could suffer head trauma, fractures, eye damage or internal bleeding. But most are stunned and simply need time to recover.
"At your house, a bird can sit by the window and recover after a little bit of time," Prince said. "But it's too dangerous downtown."
That's why Marina Post of Chicago has volunteered as a collision monitor for five years.
"It's very gratifying to feel like I'm making a difference to even a few birds," she said. "You know that you're saving them from sure demise and getting them safely on their way."
Birds that recover at Willowbrook are released into the forest preserve where they can rest and eat before resuming their migratory journeys.
"We have trees, prairie, water and a savanna," Fejt said. "So we've got a perfect little habitat. They can stay here, feed for a few days and then their instincts will tell them when it's time to move on."
Being released in a suburban forest preserve doesn't hamper the birds' ability to reach their destinations.
"These birds have an internal guidance that brought them all the way here from South America," Prince said. "Even after going 30 miles to a Western suburb, they still get to almost the exact tree they used last year in Canada."