All the deaths took place in a single day, raising concerns about the sustainability of buildings.
The birds were collected by scientists and civil society members from McCormick Place Lakeside Center.
Numbers Surpassed Previous Record
The recent numbers surpassed the previous record by three times, a bird monitoring group told BBC.
Annette Prince, the director of Bird Collision Monitors said they found around 700-800 birds in a single square mile.
McCormick Place tweeted that the previous record was around 300 a day and they were “truly saddened by the incident”.
Why Did The Birds Die?
There are multiple reasons for why the birds collided with the buildings.
The BBC reported that unusual migration patterns due to climate change and bad weather are some of the reasons.
Climate activists have also been urging buildings to reduce bright lights which can distract birds while flying at night.