Sandhill cranes fly over Chicago on Wednesday near a plane. View Full Caption Facebook/Scott Judd

CHICAGO — Chicago birders went wild Wednesday when thousands of sandhill cranes flew over the city.

The birds were a rare sight over city limits a decade ago, but they've become far more common lately due to protection of their wetland habitat.

Members in the IL Birders Exchanging Thoughts group reported seeing the birds over Lincoln Park Zoo, Old Town School of Music, Soldier Field, other Lake Michigan spots, Bucktown (Damen and North), West Ridge, University of Chicago and elsewhere in the city. Some of the birders estimated as many as 30,000 cranes flew over the city Wednesday.

Reports on Thursday said thousands of the birds appeared over Chicago.

The cranes were a hit with non-birders too — Facebook lit up with comments from folks curious about the unusual ruckus in the sky.

"I heard them all day today and had no idea what birds would make that sound! So cool!," one Lincoln Square neighbor posted to a community Facebook page.

If winds continue from the west, it's possible more of the cranes could be spotted on Thursday, according to Josh Engel, a research assistant at the Field Museum.

They can be distinguished from flocks of plain old geese courtesy of their unusual loud "rattling bugle calls" that can be heard hundreds, if not thousands of feet, away.

Like the other hundreds of thousands of birds that pass through Chicago each year, the sandhill cranes fly south over the city in the fall/winter and head north in the spring.

In the past, the sandhill's migration has typically peaked in November, but a mild fall may have pushed the cranes' flight into December, Engel told DNAinfo via email.

"Their migration has been getting gradually later for years because of generally warmer weather," he said.

"They've also been getting more abundant, so they are becoming ever more visible. It's a real treat to see them, especially in numbers like [Wednesday]. We saw almost 2,000 over the Field Museum," Engel said.

The birds breed further north and west of Chicago. Wednesday's flocks were potentially traveling from as far north as Ontario, Canada, having made stops in Minnesota and Wisconsin along their trip south.

The cranes rarely land in Chicago, instead resting up at the Jasper-Pulaski Fish and Wildlife Area in Indiana before winging their way to their winter homes in Georgia and Florida.

During a count taken Sunday at Jasper-Pulaski, 12,530 sandhill cranes were on site.

There have been documented pairs of the birds nesting in Illinois since 1987, but prior to that, there hadn't been nesting pairs in the state since 1887.

Sandhill cranes are very large birds that are gray with red skin on their crowns and black legs. In the air, they are better identified by sound than sight.

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