The annual Audubon Bird Count: it happens every year and it has been helping experts keep data on rare and migratory species for well over a century. This year, during the 115th Christmas Bird Count, participants in Chicago were treated to a series of stunning displays, where large migratory birds were spotted traveling uncharacteristically late in this season.

Some of these last-minute travelers were identified as Sandhill Cranes - an impressive species of bird that is sometimes mistaken for a Great Blue Heron and spends half the year in colder US climes. However, as winter sets in, most of these birds (save for the non-migratory Floridian subspecies) pick up and head south.

That's why just last year, Christmas Bird Count (CBC) participants from all over only reported seeing a maximum of six migratory Sandhill Cranes at one time. However, in what CBC organizer Joel Greenberg is calling "extraordinary," Chicago-area watchers spotted a stunning 900 of these birds in flight.

"By middle to end of December in northern Illinois, they're usually gone. So to get big flights this late is unusual. If it was in March or October or November, it wouldn't have been; but being late December, it's unusual," he reiterated to CBS Chicago. (Scroll to read on...)

So what's going on here? Some experts have argued in the past that climate change is effecting the timing and length of bird migrations, where a warming northern climate is delaying departures, and changing precipitations patterns are ruining "pit stops" essential for long journeys. In cases like that, it may be come down to a case of "detour or die" for long-distance migratory flocks.

Still, in the case of the Sandhill, which uses a very diverse selection of habitats, this may have just been a simple coincidence for lucky bird watchers.

Greenberg added that on New Year's Day, his group was in for another treat, spotting three bald eagles in Lake County - also an unusual sight for this time of year. In that case the bird watcher thinks that it was more a sign of the encouraging recovery of Bald Eagle populations over the last decade. The majestic bird of prey were initially threatened by hunting and unintentional DDT poisonings, but those actions have long been stopped. Bald eagles were last identified to have a healthy and increasing North American presence back in 2004.

Most CBC events in the US start anywhere after Dec. 14, and often stretch into the first week of the New Year. At its very end, counting bird watchers submit their observations online, and the data in collected to help experts measure how a region's bird populations have changed over the past hundred years.

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