WARSAW, Poland (AP) — A Polish environmental group that was using a mobile-phone transmitter to track migratory movements of a stork has received a phone bill of 10,000 zlotys ($2,650) after the bird went missing in Sudan and someone started using the chip to make calls.

Like many other storks who nest in Poland in the summer, Kajtek, an adult stork, began his southward migration to Africa in August 2017. Thanks to a SIM-chip transmitter, the Ecological Group was able to track his GPS movements and post details about the journey online .

The bird's last signal came from Sudan on April 26. But later, the group heard that some 20 hours of calls had been made using the SIM card in Sudan.

Ireneusz Kaluga, the association's head, said Friday that Kajtek "probably isn't alive."