Final answer:
The strategy used to rescue Illinois prairie chickens from extinction vortex was the establishment of a nest protection program.
Step-by-step explanation:
The strategy used to rescue Illinois prairie chickens from a recent extinction vortex was the establishment of a nest protection program. This program involved monitoring and protecting nests of globally threatened or near-threatened species, including prairie chickens. The International Crane Foundation has successfully implemented a similar strategy to raise the population of whooping cranes. By wearing crane costumes, biologists were able to imprint hatchlings and prevent them from seeing humans. This approach has been instrumental in increasing the number of whooping cranes.